auto merge of #5880 : Dretch/rust/signals, r=thestinger
auto merge of #5880 : Dretch/rust/signals, r=thestinger

This is a follow-up to #5761. Its purpose is to make core::libc more consistent - it currently only defines SIGKILL and SIGTERM, because they are the only values that happen to be needed by libcore.

This adds all the posix signal value constants, except for those that have different values on different architectures.

The output of the command `man 7 signal` was used to compile these signal values.

fabricedesre/rust,gifnksm/rust,mitsuhiko/rust,pshc/rust,kwantam/rust,krzysz00/rust,dwillmer/rust,miniupnp/rust,ruud-v-a/rust,ktossell/rust,mdinger/rust,zaeleus/rust,omasanori/rust,pelmers/rust,servo/rust,barosl/rust,nham/rust,servo/rust,pczarn/rust,jbclements/rust,jashank/rust,GBGamer/rust,mahkoh/rust,miniupnp/rust,aturon/rust,erickt/rust,barosl/rust,ebfull/rust,avdi/rust,robertg/rust,untitaker/rust,servo/rust,victorvde/rust,rohitjoshi/rust,krzysz00/rust,quornian/rust,aidancully/rust,quornian/rust,untitaker/rust,mvdnes/rust,kmcallister/rust,mdinger/rust,jroesch/rust,j16r/rust,sarojaba/rust-doc-korean,bombless/rust,stepancheg/rust-ide-rust,AerialX/rust,untitaker/rust,jbclements/rust,kmcallister/rust,emk/rust,ruud-v-a/rust,omasanori/rust,avdi/rust,aidancully/rust,erickt/rust,mahkoh/rust,nwin/rust,jroesch/rust,AerialX/rust-rt-minimal,pythonesque/rust,robertg/rust,miniupnp/rust,graydon/rust,aidancully/rust,seanrivera/rust,P1start/rust,zaeleus/rust,jashank/rust,defuz/rust,ejjeong/rust,graydon/rust,P1start/rust,0x73/rust,servo/rust,seanrivera/rust,l0kod/rust,erickt/rust,aneeshusa/rust,kwantam/rust,AerialX/rust,kimroen/rust,pczarn/rust,zubron/rust,rprichard/rust,sae-bom/rust,barosl/rust,Ryman/rust,achanda/rand,kwantam/rust,emk/rust,zaeleus/rust,P1start/rust,graydon/rust,zachwick/rust,stepancheg/rust-ide-rust,mitsuhiko/rust,jashank/rust,vhbit/rust,GrahamDennis/rand,aturon/rust,P1start/rust,kmcallister/rust,LeoTestard/rust,richo/rust,arthurprs/rand,robertg/rust,hauleth/rust,dinfuehr/rust,cllns/rust,stepancheg/rust-ide-rust,seanrivera/rust,LeoTestard/rust,quornian/rust,victorvde/rust,mdinger/rust,kmcallister/rust,reem/rust,nham/rust,vhbit/rust,krzysz00/rust,sae-bom/rust,fabricedesre/rust,pelmers/rust,XMPPwocky/rust,rprichard/rust,l0kod/rust,philyoon/rust,pythonesque/rust,mihneadb/rust,sarojaba/rust-doc-korean,carols10cents/rust,sae-bom/rust,sae-bom/rust,dinfuehr/rust,Ryman/rust,0x73/rust,jashank/rust,aturon/rust,cllns/rust,mihneadb/rust,erickt/rust,ruud-v-a/rust,hauleth/rust,aneeshusa/rust,erickt/rust,nwin/rust,jashank/rust,shepmaster/rand,quornian/rust,bombless/rust,hauleth/rust,zachwick/rust,ebfull/rand,zaeleus/rust,mahkoh/rust,zubron/rust,jbclements/rust,nwin/rust,GBGamer/rust,zaeleus/rust,fabricedesre/rust,dinfuehr/rust,philyoon/rust,sae-bom/rust,nwin/rust,TheNeikos/rust,zubron/rust,victorvde/rust,philyoon/rust,AerialX/rust,barosl/rust,mvdnes/rust,mitsuhiko/rust,gifnksm/rust,cllns/rust,Ryman/rust,pczarn/rust,dwillmer/rust,pshc/rust,miniupnp/rust,AerialX/rust,nwin/rust,pelmers/rust,reem/rust,avdi/rust,Ryman/rust,kmcallister/rust,dwillmer/rust,l0kod/rust,TheNeikos/rust,kmcallister/rust,waynenilsen/rand,miniupnp/rust,ebfull/rust,graydon/rust,sarojaba/rust-doc-korean,cllns/rust,SiegeLord/rust,untitaker/rust,michaelballantyne/rust-gpu,andars/rust,cllns/rust,aepsil0n/rust,pczarn/rust,fabricedesre/rust,rohitjoshi/rust,j16r/rust,huonw/rand,pelmers/rust,omasanori/rust,nham/rust,j16r/rust,richo/rust,bombless/rust-docs-chinese,LeoTestard/rust,jroesch/rust,P1start/rust,miniupnp/rust,mvdnes/rust,seanrivera/rust,zubron/rust,l0kod/rust,pshc/rust,jashank/rust,avdi/rust,0x73/rust,mvdnes/rust,ejjeong/rust,pythonesque/rust,aepsil0n/rust,aidancully/rust,ejjeong/rust,carols10cents/rust,mahkoh/rust,jroesch/rust,graydon/rust,dinfuehr/rust,GBGamer/rust,AerialX/rust-rt-minimal,aturon/rust,emk/rust,aepsil0n/rust,gifnksm/rust,rprichard/rust,stepancheg/rust-ide-rust,krzysz00/rust,aneeshusa/rust,mihneadb/rust,kimroen/rust,andars/rust,victorvde/rust,pczarn/rust,emk/rust,nham/rust,nham/rust,barosl/rust,zachwick/rust,seanrivera/rust,robertg/rust,vhbit/rust,mvdnes/rust,mihneadb/rust,andars/rust,andars/rust,gifnksm/rust,ejjeong/rust,pelmers/rust,richo/rust,zaeleus/rust,ejjeong/rust,quornian/rust,nwin/rust,carols10cents/rust,ktossell/rust,jroesch/rust,reem/rust,zubron/rust,hauleth/rust,j16r/rust,KokaKiwi/rust,pythonesque/rust,TheNeikos/rust,jroesch/rust,j16r/rust,krzysz00/rust,ktossell/rust,P1start/rust,richo/rust,dwillmer/rust,rohitjoshi/rust,servo/rust,rohitjoshi/rust,dwillmer/rust,GBGamer/rust,fabricedesre/rust,vhbit/rust,ebfull/rust,zachwick/rust,graydon/rust,kimroen/rust,aepsil0n/rust,hauleth/rust,erickt/rust,0x73/rust,KokaKiwi/rust,nwin/rust,mdinger/rust,nham/rust,AerialX/rust,dwillmer/rust,miniupnp/rust,cllns/rust,vhbit/rust,mdinger/rust,pelmers/rust,sarojaba/rust-doc-korean,gifnksm/rust,servo/rust,dwillmer/rust,TheNeikos/rust,ruud-v-a/rust,michaelballantyne/rust-gpu,jbclements/rust,ruud-v-a/rust,KokaKiwi/rust,mitsuhiko/rust,seanrivera/rust,kimroen/rust,0x73/rust,AerialX/rust-rt-minimal,kwantam/rust,defuz/rust,KokaKiwi/rust,pythonesque/rust,ktossell/rust,XMPPwocky/rust,mahkoh/rust,l0kod/rust,mitsuhiko/rust,philyoon/rust,jbclements/rust,aidancully/rust,reem/rust,Ryman/rust,andars/rust,zubron/rust,Ryman/rust,bombless/rust,zubron/rust,ktossell/rust,sae-bom/rust,SiegeLord/rust,omasanori/rust,LeoTestard/rust,zachwick/rust,pshc/rust,jbclements/rust,sarojaba/rust-doc-korean,pythonesque/rust,jashank/rust,quornian/rust,mvdnes/rust,vhbit/rust,omasano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