asm: fix error messages and comments for "register pair"
asm: fix error messages and comments for "register pair"

The parser treats (R1+R2) on ppc64 the same as (R1,R2) on arm,
but it is not strictly a "register pair". Improve the text.

No semantic change.

Change-Id: Ib8b14881c6467add0d53150a901c01e962afb28b
Reviewed-on: https://go-review.googlesource.com/12212
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

agaurav/go,jonahglover/go,dterei/go,nakedgc/go,PoohSunny/go,CAFxX/go,jasonxiong/go,josharian/go,Endika/go,miolini/go,sinuos/go,yangzhongj/go,akutz/go,pgmreddy/go,Cofyc/go,xujianhai/go,andrewchambers/go,GeorgiCodes/go,alash3al/go,jonathanmarvens/go,youprofit/go,xinhuang327/go,myPublicGit/go,linux-on-ibm-z/go,josharian/go,jameskumar/go,slavau/go,royels/go,suncycheng/go,jmptrader/go,zhangg/go,jasonxiong/go,jacobhaven/go,chinanjjohn2012/go,gohin/go,NunoEdgarGub1/go,gdey/go,Young55555/go,constantine001/go,miolini/go,cloudflare/go,CodyGuo/go,ganboing/go-esx,dkolbly/go,Jordanzuo/go,devpadawan/go,mwhudson/go,mgyenik/go,jacobhaven/go,skotti/go,vsdutka/go,pgmreddy/go,shines77/go,Pulgafree/go,jameskumar/go,kakuhiroshi/go,joshsammut/go,agaurav/go,linux-on-ibm-z/go,theass/go,yeyuguo/go,jdeng/go,jdhenke/go,Stan-Lin-/go,undergrowthlinear/go,joshsammut/go,jdhenke/go,vsekhar/elastic-go,springning/go,jonathanmarvens/go,Jordanzuo/go,skotti/go,danycoro/go,goodlang/good,dpatel06/go,dpatel06/go,Young55555/go,skatsuta/go,Stan-Lin-/go,kim-racktop/go,CodyGuo/go,NunoEdgarGub1/go,pgmreddy/go,NichoZhang/go,yeyuguo/go,sosop/go,vsekhar/elastic-go,stormltf/go,youprofit/go,parkdy/go,likesea/go,xujianhai/go,youprofit/go,arschles/go-1,jonathanmarvens/go,CAFxX/go,jdeng/go,sndnvaps/go,shazow/go,jonasi/go,4ad/go,CodyGuo/go,sinuos/go,nawawi/go,alex-zhang/go,jefby/go,Cofyc/go,sinuos/go,RBEGamer/go,sinuos/go,CiscoCloud/go,CarterTsai/go,jonahglover/go,chinanjjohn2012/go,Jordanzuo/go,gdey/go,CiscoCloud/go,kakuhiroshi/go,golang/go,rachtsingh/gogojuice,qskycolor/go,XuYunnan/go,donnel6809/go,vishsingh/go,JioCloud/go,myPublicGit/go,monetate/go,leeric92/go,undergrowthlinear/go,mikekap/go,ErikDubbelboer/go,codestation/go,constantine001/go,JioCloud/go,JioCloud/go,likesea/go,kakuhiroshi/go,Cofyc/go,samanalysis/go,skatsuta/go,g522342435/go,ImJasonH/go,akutz/go,zouchao2010/go,Samurais/go,parkdy/go,likesea/go,andrewchambers/go,stormltf/go,jdhenke/go,alex-zhang/go,arschles/go-1,zhangg/go,honsiorovskyi/go,cloudrain21/go,mbrukman/go,nawawi/go,zouchao2010/go,cyberroadie/go,dgnorton/go,shishkander/go,donnel6809/go,xiaobodu/go,polyverse-security/go,xiaobodu/go,Charlesdong/go-1,constantine001/go,skotti/go,ganboing/go-esx,yuhengye/go,jacobsa/go,dterei/go,yuhengye/go,parkdy/go,RBEGamer/go,albertjin/golang-go,ObjectiveJoe/go,skotti/go,mbrukman/go,rachtsingh/gogojuice,Cofyc/go,GeorgiCodes/go,nakedgc/go,ericsnowcurrently/go,theass/go,roth1002/go,jdeng/go,NichoZhang/go,shines77/go,Cofyc/go,xinhuang327/go,myPublicGit/go,joshsammut/go,kim-racktop/go,skatsuta/go,willjunspecial/go,skotti/go,Charlesdong/go-1,sinuos/go,malvira/go,RBEGamer/go,arschles/golang-go,odeke-em/go,alex-zhang/go,nakedgc/go,malvira/go,jonathanmarvens/go,nakedgc/go,golang/go,ichu501/go,binarycrusader/go,xiuzhifu/go,binarycrusader/go,yeyuguo/go,theass/go,honsiorovskyi/go,jdhenke/go,greyhwndz/go,mdp/go,leeric92/go,mwhudson/go,yuhengye/go,stormltf/go,dafyddcrosby/go,snowsnail/go,suncycheng/go,skotti/go,snowsnail/go,Charlesdong/go-1,theif519/go,mwhudson/go,cloudrain21/go,Badredapple/go,akutz/go,yasarkunduz/go,RBEGamer/go,danielsoro/go,monetate/go,greyhwndz/go,donnel6809/go,parkdy/go,Endika/go,samanalysis/go,GeorgiCodes/go,cookerzhu/go,Badredapple/go,likesea/go,zcwfeng/go,ganboing/go-esx,CAFxX/go,pgmreddy/go,derekmarcotte/go,devpadawan/go,WIZARD-CXY/go,zcwfeng/go,ImJasonH/go,jmptrader/go,jasonxiong/go,yangzhongj/go,ericsnowcurrently/go,ifagnosticism/go,parkdy/go,alash3al/go,rachtsingh/gogojuice,slavau/go,gohin/go,akutz/go,chinanjjohn2012/go,xiuzhifu/go,jacobsa/go,AALEKH/go,CodyGuo/go,jonathanmarvens/go,qskycolor/go,jacobxk/go,jmptrader/go,kim-racktop/go,myPublicGit/go,ifagnosticism/go,CiscoCloud/go,sndnvaps/go,willjunspecial/go,cookerzhu/go,alex-zhang/go,yeyuguo/go,yasarkunduz/go,mbrukman/go,codestation/go,jefby/go,Young55555/go,pgmreddy/go,kakuhiroshi/go,famorted/go,GeorgiCodes/go,yangzhongj/go,PoohSunny/go,mwhudson/go,baiyunping333/go,beealone/go,RBEGamer/go,deft-code/go,NunoEdgarGub1/go,polyverse-security/go,zcwfeng/go,derekmarcotte/go,mdp/go,ganboing/go-esx,vsekhar/elastic-go,Samurais/go,mikekap/go,yasarkunduz/go,wangfakang/go-1,skatsuta/go,lihuanghai/go,ganboing/go-esx,albertjin/golang-go,CAFxX/go,nawawi/go,binarycrusader/go,PoohSunny/go,chinanjjohn2012/go,zouchao2010/go,mgyenik/go,xujianhai/go,CiscoCloud/go,sosop/go,suncycheng/go,akutz/go,Charlesdong/go-1,gohin/go,9618211/go,theif519/go,dterei/go,theif519/go,rentongzhang/go,ichu501/go,momchil-velikov/go,mwhudson/go,mdp/go,shishkander/go,9618211/go,ImJasonH/go,deft-code/go,b54898533/go,arschles/go-1,greyhwndz/go,ichu501/go,AALEKH/go,jefby/go,g522342435/go,weisd/go,jonahglover/go,XuYunnan/go,rentongzhang/go,royels/go,fjballest/golang,uileyar/go,undergrowthlinear/go,WIZARD-CXY/go,mdp/go,snowsnail/go,leeric92/go,arschles/go-1,sosop/go,cyberroadie/go,jameskumar/go,albertjin/golang-go,dkolbly/go,AALEKH/go,yeyuguo/go,yangzhongj/go,snowsnail/go,cainiaocome/go,jacobhaven/go,mikekap/go,kevinc0825/go,nakedgc/go,skatsuta/go,CodyGuo/go,leeric92/go,xujianhai/go,danycoro/go,skatsuta/go,jacobsa/go,jdhenke/go,zouchao2010/go,samanalysis/go,sndnvaps/go,undergrowthlinear/go,jacobsa/go,slavau/go,dterei/go,sndnvaps/go,golang/go,ImJasonH/go,CAFxX/go,cyberroadie/go,golang/go,RBEGamer/go,constantine001/go,uileyar/go,NichoZhang/go,NunoEdgarGub1/go,cookerzhu/go,cloudrain21/go,ericsnowcurrently/go,sndnvaps/go,rentongzhang/go,danycoro/go,dpatel06/go,qskycolor/go,jacobxk/go,cloudflare/go,AALEKH/go,qskycolor/go,codestation/go,kevinc0825/go,binarycrusader/go,famorted/go,codestation/go,theass/go,springning/go,odeke-em/go,ichu501/go,Badredapple/go,b54898533/go,XuYunnan/go,cainiaocome/go,cloudflare/go,roth1002/go,CiscoCloud/go,WIZARD-CXY/go,uileyar/go,chinanjjohn2012/go,vsekhar/elastic-go,CiscoCloud/go,theass/go,cyberroadie/go,Endika/go,b54898533/go,greyhwndz/go,myPublicGit/go,xujianhai/go,cainiaocome/go,XuYunnan/go,pgmreddy/go,chinanjjohn2012/go,jonasi/go,cnbin/go,codestation/go,arschles/go-1,jdhenke/go,goodlang/good,linux-on-ibm-z/go,dterei/go,constantine001/go,dterei/go,zouchao2010/go,stormltf/go,ErikDubbelboer/go,goodlang/good,PoohSunny/go,9618211/go,albertjin/golang-go,dkolbly/go,4ad/go,honsiorovskyi/go,beealone/go,mgyenik/go,baiyunping333/go,ericsnowcurrently/go,youprofit/go,xujianhai/go,zhangg/go,dgnorton/go,fjballest/golang,alex-zhang/go,xujianhai/go,shazow/go,polyverse-security/go,ganboing/go-esx,likesea/go,goodlang/good,linux-on-ibm-z/go,springning/go,dgnorton/go,theass/go,jonathanmarvens/go,pgmreddy/go,undergrowthlinear/go,royels/go,AALEKH/go,leeric92/go,deft-code/go,xinhuang327/go,Young55555/go,likesea/go,cloudrain21/go,weisd/go,Endika/go,kakuhiroshi/go,ericsnowcurrently/go,samanalysis/go,WIZARD-CXY/go,mikekap/go,dkolbly/go,mikekap/go,kevinc0825/go,sosop/go,danycoro/go,dpatel06/go,lihuanghai/go,mgyenik/go,b54898533/go,Cofyc/go,dafyddcrosby/go,linux-on-ibm-z/go,vishsingh/go,g522342435/go,CarterTsai/go,yeyuguo/go,danielsoro/go,derekmarcotte/go,4ad/go,yeyuguo/go,baiyunping333/go,sinuos/go,vsekhar/elastic-go,jefby/go,dafyddcrosby/go,wangfakang/go-1,CiscoCloud/go,samanalysis/go,jonasi/go,jmptrader/go,ichu501/go,uileyar/go,stormltf/go,kevinc0825/go,royels/go,cnbin/go,kakuhiroshi/go,NunoEdgarGub1/go,JioCloud/go,Samurais/go,ErikDubbelboer/go,josharian/go,vishsingh/go,deft-code/go,jasonxiong/go,binarycrusader/go,derekmarcotte/go,jasonxiong/go,josharian/go,ericsnowcurrently/go,xiaobodu/go,binarycrusader/go,cainiaocome/go,jacobsa/go,ErikDubbelboer/go,beealone/go,ErikDubbelboer/go,suncycheng/go,danielsoro/go,dgnorton/go,cloudrain21/go,cookerzhu/go,josharian/go,undergrowthlinear/go,mdp/go,PoohSunny/go,g522342435/go,agaurav/go,cnbin/go,wangfakang/go-1,vishsingh/go,Endika/go,b54898533/go,beealone/go,vsdutka/go,josharian/go,vanloswang/go,cnbin/go,devpadawan/go,GeorgiCodes/go,dpatel06/go,xiuzhifu/go,CodyGuo/go,yasarkunduz/go,qskycolor/go,lihuanghai/go,andrewchambers/go,4ad/go,kevinc0825/go,g522342435/go,cookerzhu/go,danielsoro/go,honsiorovskyi/go,slavau/go,cyberroadie/go,cookerzhu/go,gohin/go,derekmarcotte/go,codestation/go,agaurav/go,deft-code/go,greyhwndz/go,shazow/go,xinhuang327/go,miolini/go,albertjin/golang-go,CarterTsai/go,derekmarcotte/go,dgnorton/go,shazow/go,AALEKH/go,NichoZhang/go,arschles/golang-go,mikekap/go,undergrowthlinear/go,rentongzhang/go,lihuanghai/go,jonasi/go,alash3al/go,gohin/go,sndnvaps/go,honsiorovskyi/go,skotti/go,roth1002/go,odeke-em/go,ganboing/go-esx,gdey/go,Young55555/go,fjballest/golang,suncycheng/go,vishsingh/go,jonasi/go,qskycolor/go,qskycolor/go,linux-on-ibm-z/go,shazow/go,jonahglover/go,agaurav/go,Samurais/go,famorted/go,momchil-velikov/go,wangfakang/go-1,ErikDubbelboer/go,gdey/go,cloudflare/go,vsekhar/elastic-go,devpadawan/go,ImJasonH/go,Stan-Lin-/go,cnbin/go,danielsoro/go,sinuos/go,theif519/go,alex-zhang/go,polyverse-security/go,Badredapple/go,Pulgafree/go,vsdutka/go,youprofit/go,theif519/go,mgyenik/go,josharian/go,shines77/go,dafyddcrosby/go,GeorgiCodes/go,JioCloud/go,alash3al/go,mbrukman/go,shishkander/go,Endika/go,theass/go,cainiaocome/go,Badredapple/go,roth1002/go,kim-racktop/go,mwhudson/go,danycoro/go,9618211/go,CAFxX/go,josharian/go,youprofit/go,andrewchambers/go,andrewchambers/go,cloudrain21/go,constantine001/go,willjunspecial/go,jdeng/go,dkolbly/go,danielsoro/go,suncycheng/go,lihuanghai/go,arschles/golang-go,XuYunnan/go,miolini/go,samanalysis/go,honsiorovskyi/go,devpadawan/go,dgnorton/go,CarterTsai/go,9618211/go,alash3al/go,nawawi/go,rachtsingh/gogojuice,mwhudson/go,honsiorovskyi/go,fjballest/golang,9618211/go,goodlang/good,wangfakang/go-1,roth1002/go,ObjectiveJoe/go,joshsammut/go,fjballest/golang,ichu501/go,zouchao2010/go,RBEGamer/go,cyberroadie/go,chinanjjohn2012/go,vishsingh/go,g522342435/go,ErikDubbelboer/go,ErikDubbelboer/go,shines77/go,arschles/golang-go,jmptrader/go,royels/go,Endika/go,fjballest/golang,kim-racktop/go,snowsnail/go,greyhwndz/go,sndnvaps/go,mikekap/go,odeke-em/go,jacobxk/go,Stan-Lin-/go,skotti/go,nakedgc/go,danycoro/go,CarterTsai/go,miolini/go,GeorgiCodes/go,yuhengye/go,cyberroadie/go,CarterTsai/go,greyhwndz/go,Stan-Lin-/go,gdey/go,CodyGuo/go,AALEKH/go,ObjectiveJoe/go,danycoro/go,snowsnail/go,ganboing/go-esx,shishkander/go,suncycheng/go,alex-zhang/go,andrewchambers/go,4ad/go,shishkander/go,vsdutka/go,constantine001/go,gohin/go,golang/go,odeke-em/go,myPublicGit/go,willjunspecial/go,jefby/go,PoohSunny/go,dgnorton/go,leeric92/go,jdeng/go,CarterTsai/go,zcwfeng/go,devpadawan/go,gohin/go,danielsoro/go,jacobxk/go,sosop/go,wangfakang/go-1,yangzhongj/go,cnbin/go,xinhuang327/go,malvira/go,JioCloud/go,xiaobodu/go,leeric92/go,jameskumar/go,skatsuta/go,agaurav/go,springning/go,NichoZhang/go,shines77/go,odeke-em/go,weisd/go,monetate/go,binarycrusader/go,dkolbly/go,NichoZhang/go,jonahglover/go,gohin/go,jameskumar/go,kevinc0825/go,dpatel06/go,cyberroadie/go,WIZARD-CXY/go,yasarkunduz/go,Young55555/go,monetate/go,arschles/go-1,binarycrusader/go,mgyenik/go,Pulgafree/go,malvira/go,momchil-velikov/go,alash3al/go,arschles/golang-go,jdeng/go,CodyGuo/go,ichu501/go,cloudrain21/go,yangzhongj/go,stormltf/go,kevinc0825/go,mikekap/go,zouchao2010/go,xiuzhifu/go,yuhengye/go,CAFxX/go,shazow/go,akutz/go,cnbin/go,dafyddcrosby/go,royels/go,christopher-henderson/Go,g522342435/go,dterei/go,beealone/go,derekmarcotte/go,zcwfeng/go,cloudflare/go,Cofyc/go,miolini/go,ObjectiveJoe/go,springning/go,xinhuang327/go,xiaobodu/go,zouchao2010/go,jacobsa/go,shishkander/go,shazow/go,lihuanghai/go,ImJasonH/go,jonahglover/go,b54898533/go,derekmarcotte/go,ImJasonH/go,nakedgc/go,jmptrader/go,Endika/go,mdp/go,jonathanmarvens/go,zhangg/go,dterei/go,myPublicGit/go,donnel6809/go,baiyunping333/go,snowsnail/go,sinuos/go,jasonxiong/go,gdey/go,jefby/go,rentongzhang/go,yuhengye/go,malvira/go,zhangg/go,ichu501/go,zhangg/go,weisd/go,Samurais/go,roth1002/go,willjunspecial/go,rentongzhang/go,Charlesdong/go-1,dgnorton/go,devpadawan/go,jameskumar/go,Stan-Lin-/go,odeke-em/go,jacobhaven/go,vanloswang/go,shines77/go,ImJasonH/go,vanloswang/go,wangfakang/go-1,monetate/go,shazow/go,baiyunping333/go,linux-on-ibm-z/go,ObjectiveJoe/go,donnel6809/go,fjballest/golang,beealone/go,kim-racktop/go,vsdutka/go,lihuanghai/go,slavau/go,Jordanzuo/go,kim-racktop/go,ifagnosticism/go,monetate/go,uileyar/go,vsdutka/go,jmptrader/go,agaurav/go,willjunspecial/go,shishkander/go,Charlesdong/go-1,golang/go,NunoEdgarGub1/go,deft-code/go,vishsingh/go,rachtsingh/gogojuice,sosop/go,dpatel06/go,akutz/go,dkolbly/go,jonasi/go,malvira/go,snowsnail/go,Young55555/go,vsekhar/elastic-go,dafyddcrosby/go,Samurais/go,mbrukman/go,zhangg/go,ifagnosticism/go,mbrukman/go,theass/go,4ad/go,jonasi/go,parkdy/go,monetate/go,slavau/go,andrewchambers/go,joshsammut/go,leeric92/go,4ad/go,jefby/go,yuhengye/go,jonahglover/go,vanloswang/go,momchil-velikov/go,jacobxk/go,agaurav/go,uileyar/go,xiaobodu/go,Jordanzuo/go,jameskumar/go,deft-code/go,arschles/go-1,yangzhongj/go,danycoro/go,cookerzhu/go,donnel6809/go,9618211/go,Pulgafree/go,famorted/go,mbrukman/go,ObjectiveJoe/go,NichoZhang/go,miolini/go,golang/go,mdp/go,Badredapple/go,b54898533/go,nawawi/go,donnel6809/go,Charlesdong/go-1,GeorgiCodes/go,youprofit/go,ifagnosticism/go,dpatel06/go,cookerzhu/go,golang/go,rachtsingh/gogojuice,alash3al/go,royels/go,Jordanzuo/go,jefby/go,xiaobodu/go,g522342435/go,JioCloud/go,Jordanzuo/go,xiuzhifu/go,Stan-Lin-/go,PoohSunny/go,shines77/go,chinanjjohn2012/go,theif519/go,Badredapple/go,gdey/go,youprofit/go,arschles/golang-go,shines77/go,xinhuang327/go,ericsnowcurrently/go,andrewchambers/go,goodlang/good,rachtsingh/gogojuice,malvira/go,roth1002/go,parkdy/go,rachtsingh/gogojuice,beealone/go,goodlang/good,kim-racktop/go,ObjectiveJoe/go,WIZARD-CXY/go,jonathanmarvens/go,xiaobodu/go,willjunspecial/go,yangzhongj/go,weisd/go,NunoEdgarGub1/go,cloudrain21/go,qskycolor/go,cloudflare/go,xujianhai/go,joshsammut/go,jonasi/go,nawawi/go,vanloswang/go,greyhwndz/go,albertjin/golang-go,polyverse-security/go,momchil-velikov/go,stormltf/go,uileyar/go,undergrowthlinear/go,shishkander/go,monetate/go,likesea/go,cloudflare/go,jdeng/go,xiuzhifu/go,willjunspecial/go,parkdy/go,PoohSunny/go,9618211/go,roth1002/go,rentongzhang/go,famorted/go,Young55555/go,devpadawan/go,alash3al/go,mbrukman/go,springning/go,baiyunping333/go,vsekhar/elastic-go,donnel6809/go,mgyenik/go,vsdutka/go,cainiaocome/go,yasarkunduz/go,slavau/go,miolini/go,Jordanzuo/go,xinhuang327/go,royels/go,CiscoCloud/go,likesea/go,dafyddcrosby/go,jacobhaven/go,cloudflare/go,akutz/go,Samurais/go,Badredapple/go,ObjectiveJoe/go,cainiaocome/go,zcwfeng/go,RBEGamer/go,momchil-velikov/go,polyverse-security/go,xiuzhifu/go,pgmreddy/go,malvira/go,theif519/go,Pulgafree/go,samanalysis/go,momchil-velikov/go,WIZARD-CXY/go,CarterTsai/go,slavau/go,mwhudson/go,linux-on-ibm-z/go,uileyar/go,codestation/go,albertjin/golang-go,odeke-em/go,AALEKH/go,honsiorovskyi/go,yeyuguo/go,joshsammut/go,vanloswang/go,springning/go,sosop/go,albertjin/golang-go,JioCloud/go,deft-code/go,Charlesdong/go-1,jacobxk/go,kakuhiroshi/go,cainiaocome/go,jmptrader/go,b54898533/go,Cofyc/go,sosop/go,CAFxX/go,ifagnosticism/go,ifagnosticism/go,ifagnosticism/go,danielsoro/go,constantine001/go,vanloswang/go,stormltf/go,NichoZhang/go,jacobhaven/go,zhangg/go,mgyenik/go,Stan-Lin-/go,Pulgafree/go,xiuzhifu/go,yasarkunduz/go,zcwfeng/go,jacobhaven/go,vanloswang/go,nawawi/go,polyverse-security/go,XuYunnan/go,NunoEdgarGub1/go,jasonxiong/go,momchil-velikov/go,jdeng/go,alex-zhang/go,arschles/golang-go,joshsammut/go,famorted/go,baiyunping333/go,kakuhiroshi/go,springning/go,jdhenke/go,kevinc0825/go,yuhengye/go,famorted/go,jacobsa/go,sndnvaps/go,Pulgafree/go,jacobhaven/go,beealone/go,jasonxiong/go,baiyunping333/go,dkolbly/go,arschles/go-1,samanalysis/go,weisd/go,vishsingh/go,4ad/go,ericsnowcurrently/go,rentongzhang/go,jacobxk/go,jonahglover/go,dafyddcrosby/go,fjballest/golang,Pulgafree/go,jdhenke/go,XuYunnan/go,mdp/go,jacobsa/go,weisd/go,suncycheng/go,nawawi/go,zcwfeng/go,skatsuta/go,famorted/go,wangfakang/go-1,weisd/go,jameskumar/go,XuYunnan/go,goodlang/good,codestation/go,jacobxk/go,lihuanghai/go,vsdutka/go,cnbin/go,theif519/go,gdey/go,arschles/golang-go,nakedgc/go,polyverse-security/go,WIZARD-CXY/go,yasarkunduz/go,Samurais/go,myPublicGit/go