runtime: avoid debug prints of huge objects
runtime: avoid debug prints of huge objects

Currently when the GC prints an object for debugging (e.g., for a
failed invalidptr or checkmark check), it dumps the entire object. To
avoid inundating the user with output for really large objects, limit
this to printing just the first 128 words (which are most likely to be
useful in identifying the type of an object) and the 32 words around
the problematic field.

Change-Id: Id94a5c9d8162f8bd9b2a63bf0b1bfb0adde83c68
Reviewed-on: https://go-review.googlesource.com/14764
Reviewed-by: Rick Hudson <838bd060584c511f21c75c69ea04b7b120d86af0@golang.org>

jacobhaven/go,linux-on-ibm-z/go,kim-racktop/go,snowsnail/go,nawawi/go,jdhenke/go,samanalysis/go,ganboing/go-esx,jdhenke/go,ganboing/go-esx,gdey/go,CAFxX/go,mikekap/go,GeorgiCodes/go,fjballest/golang,polyverse-security/go,samanalysis/go,GeorgiCodes/go,4ad/go,ganboing/go-esx,likesea/go,jacobhaven/go,jonasi/go,theif519/go,Pulgafree/go,malvira/go,alex-zhang/go,ganboing/go-esx,polyverse-security/go,miolini/go,sndnvaps/go,odeke-em/go,Samurais/go,odeke-em/go,NunoEdgarGub1/go,Endika/go,gdey/go,jdhenke/go,miolini/go,momchil-velikov/go,fjballest/golang,vsekhar/elastic-go,jdhenke/go,josharian/go,Pulgafree/go,goodlang/good,alex-zhang/go,cookerzhu/go,mwhudson/go,linux-on-ibm-z/go,Samurais/go,joshsammut/go,GeorgiCodes/go,Cofyc/go,jacobhaven/go,fjballest/golang,NunoEdgarGub1/go,theif519/go,ganboing/go-esx,vsekhar/elastic-go,mikekap/go,deft-code/go,jacobhaven/go,goodlang/good,jonasi/go,vsekhar/elastic-go,theif519/go,theif519/go,CAFxX/go,roth1002/go,ganboing/go-esx,kim-racktop/go,cyberroadie/go,Cofyc/go,mwhudson/go,theif519/go,jacobsa/go,akutz/go,mwhudson/go,snowsnail/go,jacobsa/go,vsekhar/elastic-go,josharian/go,alex-zhang/go,nawawi/go,linux-on-ibm-z/go,ichu501/go,malvira/go,4ad/go,linux-on-ibm-z/go,CarterTsai/go,cloudflare/go,Endika/go,NunoEdgarGub1/go,CarterTsai/go,ImJasonH/go,gdey/go,ichu501/go,Jordanzuo/go,Cofyc/go,odeke-em/go,jonasi/go,GeorgiCodes/go,cookerzhu/go,nawawi/go,CarterTsai/go,akutz/go,cloudflare/go,polyverse-security/go,roth1002/go,Samurais/go,Jordanzuo/go,GeorgiCodes/go,joshsammut/go,samanalysis/go,odeke-em/go,Jordanzuo/go,kim-racktop/go,joshsammut/go,golang/go,alex-zhang/go,cyberroadie/go,jacobhaven/go,mwhudson/go,Jordanzuo/go,snowsnail/go,rachtsingh/gogojuice,Samurais/go,codestation/go,beealone/go,mikekap/go,josharian/go,malvira/go,4ad/go,Jordanzuo/go,jdhenke/go,miolini/go,rachtsingh/gogojuice,goodlang/good,samanalysis/go,xiuzhifu/go,derekmarcotte/go,xiuzhifu/go,dterei/go,vanloswang/go,kim-racktop/go,jacobsa/go,golang/go,mwhudson/go,josharian/go,gdey/go,Endika/go,Jordanzuo/go,vanloswang/go,akutz/go,roth1002/go,Samurais/go,miolini/go,rachtsingh/gogojuice,linux-on-ibm-z/go,cyberroadie/go,goodlang/good,fjballest/golang,rachtsingh/gogojuice,polyverse-security/go,josharian/go,rachtsingh/gogojuice,binarycrusader/go,binarycrusader/go,goodlang/good,Cofyc/go,nawawi/go,beealone/go,snowsnail/go,theif519/go,gdey/go,joshsammut/go,Jordanzuo/go,gdey/go,CarterTsai/go,cloudflare/go,golang/go,goodlang/good,likesea/go,joshsammut/go,likesea/go,codestation/go,miolini/go,CAFxX/go,deft-code/go,linux-on-ibm-z/go,roth1002/go,beealone/go,GeorgiCodes/go,ichu501/go,yasarkunduz/go,Cofyc/go,akutz/go,cyberroadie/go,suncycheng/go,binarycrusader/go,momchil-velikov/go,b54898533/go,ImJasonH/go,alex-zhang/go,4ad/go,suncycheng/go,binarycrusader/go,jonasi/go,snowsnail/go,sndnvaps/go,xiuzhifu/go,cookerzhu/go,derekmarcotte/go,beealone/go,jonasi/go,nawawi/go,nawawi/go,malvira/go,fjballest/golang,GeorgiCodes/go,snowsnail/go,polyverse-security/go,cyberroadie/go,josharian/go,derekmarcotte/go,mikekap/go,momchil-velikov/go,rachtsingh/gogojuice,linux-on-ibm-z/go,cookerzhu/go,malvira/go,GeorgiCodes/go,samanalysis/go,nawawi/go,sndnvaps/go,akutz/go,snowsnail/go,golang/go,fjballest/golang,cookerzhu/go,CAFxX/go,mikekap/go,Endika/go,roth1002/go,snowsnail/go,kim-racktop/go,dterei/go,CarterTsai/go,deft-code/go,4ad/go,vanloswang/go,vanloswang/go,ImJasonH/go,derekmarcotte/go,jacobhaven/go,Cofyc/go,likesea/go,polyverse-security/go,deft-code/go,beealone/go,yasarkunduz/go,vanloswang/go,b54898533/go,golang/go,suncycheng/go,jonasi/go,jacobsa/go,gdey/go,xiuzhifu/go,Endika/go,cyberroadie/go,vanloswang/go,jonasi/go,CAFxX/go,suncycheng/go,momchil-velikov/go,yasarkunduz/go,joshsammut/go,sndnvaps/go,CAFxX/go,b54898533/go,beealone/go,yasarkunduz/go,dterei/go,samanalysis/go,cookerzhu/go,ganboing/go-esx,momchil-velikov/go,vanloswang/go,suncycheng/go,kim-racktop/go,dterei/go,alex-zhang/go,deft-code/go,Pulgafree/go,Pulgafree/go,b54898533/go,mwhudson/go,momchil-velikov/go,rachtsingh/gogojuice,josharian/go,polyverse-security/go,CarterTsai/go,likesea/go,Pulgafree/go,alex-zhang/go,odeke-em/go,linux-on-ibm-z/go,mikekap/go,CarterTsai/go,cloudflare/go,theif519/go,beealone/go,yasarkunduz/go,codestation/go,cloudflare/go,ImJasonH/go,ichu501/go,deft-code/go,mwhudson/go,jdhenke/go,ImJasonH/go,mwhudson/go,cookerzhu/go,suncycheng/go,NunoEdgarGub1/go,xiuzhifu/go,vsekhar/elastic-go,miolini/go,Samurais/go,4ad/go,cloudflare/go,sndnvaps/go,momchil-velikov/go,jdhenke/go,suncycheng/go,Endika/go,miolini/go,goodlang/good,Pulgafree/go,b54898533/go,ImJasonH/go,yasarkunduz/go,Cofyc/go,ganboing/go-esx,Samurais/go,dterei/go,Jordanzuo/go,jacobhaven/go,nawawi/go,malvira/go,derekmarcotte/go,gdey/go,vsekhar/elastic-go,NunoEdgarGub1/go,golang/go,polyverse-security/go,ichu501/go,theif519/go,cyberroadie/go,beealone/go,derekmarcotte/go,ichu501/go,goodlang/good,fjballest/golang,josharian/go,binarycrusader/go,4ad/go,binarycrusader/go,CAFxX/go,odeke-em/go,momchil-velikov/go,vsekhar/elastic-go,binarycrusader/go,dterei/go,akutz/go,Pulgafree/go,jacobsa/go,roth1002/go,xiuzhifu/go,akutz/go,odeke-em/go,likesea/go,deft-code/go,suncycheng/go,vanloswang/go,cyberroadie/go,CAFxX/go,deft-code/go,Endika/go,yasarkunduz/go,golang/go,mikekap/go,ichu501/go,codestation/go,rachtsingh/gogojuice,fjballest/golang,golang/go,christopher-henderson/Go,vsekhar/elastic-go,joshsammut/go,dterei/go,jonasi/go,odeke-em/go,codestation/go,Endika/go,dterei/go,cookerzhu/go,NunoEdgarGub1/go,cloudflare/go,xiuzhifu/go,sndnvaps/go,b54898533/go,kim-racktop/go,jacobsa/go,codestation/go,Cofyc/go,jdhenke/go,akutz/go,yasarkunduz/go,NunoEdgarGub1/go,NunoEdgarGub1/go,samanalysis/go,likesea/go,codestation/go,binarycrusader/go,CarterTsai/go,derekmarcotte/go,roth1002/go,jacobsa/go,xiuzhifu/go,b54898533/go,4ad/go,malvira/go,Samurais/go,sndnvaps/go,jacobhaven/go,ichu501/go,ImJasonH/go,alex-zhang/go,likesea/go,cloudflare/go,sndnvaps/go,codestation/go,miolini/go,samanalysis/go,Pulgafree/go,joshsammut/go,malvira/go,roth1002/go,mikekap/go,derekmarcotte/go,kim-racktop/go,ImJasonH/go,b54898533/go,jacobsa/go