base64: clarify signedness in negative initialization
base64: clarify signedness in negative initialization

Some platforms do not use signed char (arm)

matt-kwong/grpc,malexzx/grpc,y-zeng/grpc,podsvirov/grpc,wcevans/grpc,ejona86/grpc,nicolasnoble/grpc,y-zeng/grpc,ncteisen/grpc,vsco/grpc,bogdandrutu/grpc,ananthonline/grpc,a-veitch/grpc,kumaralokgithub/grpc,arkmaxim/grpc,PeterFaiman/ruby-grpc-minimal,hstefan/grpc,zhimingxie/grpc,philcleveland/grpc,vjpai/grpc,tamihiro/grpc,msiedlarek/grpc,ncteisen/grpc,apolcyn/grpc,grpc/grpc,chrisdunelm/grpc,a11r/grpc,quizlet/grpc,wcevans/grpc,Crevil/grpc,geffzhang/grpc,jcanizales/grpc,yongni/grpc,grpc/grpc,dklempner/grpc,murgatroid99/grpc,soltanmm-google/grpc,ppietrasa/grpc,thinkerou/grpc,grani/grpc,nicolasnoble/grpc,stanley-cheung/grpc,leifurhauks/grpc,ncteisen/grpc,LuminateWireless/grpc,7anner/grpc,grani/grpc,andrewpollock/grpc,pmarks-net/grpc,soltanmm/grpc,MakMukhi/grpc,kumaralokgithub/grpc,kumaralokgithub/grpc,msmania/grpc,soltanmm/grpc,carl-mastrangelo/grpc,ncteisen/grpc,fuchsia-mirror/third_party-grpc,ctiller/grpc,andrewpollock/grpc,tengyifei/grpc,tengyifei/grpc,soltanmm/grpc,pmarks-net/grpc,a11r/grpc,dgquintas/grpc,ipylypiv/grpc,jtattermusch/grpc,PeterFaiman/ruby-grpc-minimal,wcevans/grpc,miselin/grpc,stanley-cheung/grpc,ejona86/grpc,matt-kwong/grpc,nicolasnoble/grpc,Crevil/grpc,adelez/grpc,jtattermusch/grpc,tengyifei/grpc,arkmaxim/grpc,grpc/grpc,jtattermusch/grpc,yongni/grpc,msmania/grpc,grani/grpc,grpc/grpc,yugui/grpc,wcevans/grpc,daniel-j-born/grpc,kpayson64/grpc,pmarks-net/grpc,grpc/grpc,murgatroid99/grpc,greasypizza/grpc,sreecha/grpc,andrewpollock/grpc,muxi/grpc,thunderboltsid/grpc,carl-mastrangelo/grpc,hstefan/grpc,philcleveland/grpc,thunderboltsid/grpc,wcevans/grpc,matt-kwong/grpc,thunderboltsid/grpc,makdharma/grpc,zhimingxie/grpc,ncteisen/grpc,jboeuf/grpc,msmania/grpc,sreecha/grpc,jtattermusch/grpc,Vizerai/grpc,tamihiro/grpc,jboeuf/grpc,thinkerou/grpc,andrewpollock/grpc,MakMukhi/grpc,hstefan/grpc,dgquintas/grpc,vsco/grpc,arkmaxim/grpc,vjpai/grpc,ncteisen/grpc,deepaklukose/grpc,msiedlarek/grpc,nicolasnoble/grpc,carl-mastrangelo/grpc,ipylypiv/grpc,sreecha/grpc,bogdandrutu/grpc,philcleveland/grpc,kriswuollett/grpc,apolcyn/grpc,zhimingxie/grpc,stanley-cheung/grpc,firebase/grpc,firebase/grpc,quizlet/grpc,sreecha/grpc,kskalski/grpc,kriswuollett/grpc,arkmaxim/grpc,carl-mastrangelo/grpc,grani/grpc,y-zeng/grpc,daniel-j-born/grpc,jcanizales/grpc,msiedlarek/grpc,jboeuf/grpc,baylabs/grpc,bogdandrutu/grpc,yang-g/grpc,donnadionne/grpc,mehrdada/grpc,muxi/grpc,PeterFaiman/ruby-grpc-minimal,miselin/grpc,bogdandrutu/grpc,msiedlarek/grpc,a11r/grpc,deepaklukose/grpc,murgatroid99/grpc,muxi/grpc,firebase/grpc,royalharsh/grpc,yang-g/grpc,greasypizza/grpc,stanley-cheung/grpc,daniel-j-born/grpc,PeterFaiman/ruby-grpc-minimal,sreecha/grpc,fuchsia-mirror/third_party-grpc,leifurhauks/grpc,pszemus/grpc,kpayson64/grpc,grpc/grpc,deepaklukose/grpc,sreecha/grpc,malexzx/grpc,thinkerou/grpc,andrewpollock/grpc,msmania/grpc,kriswuollett/grpc,tengyifei/grpc,leifurhauks/grpc,dgquintas/grpc,firebase/grpc,royalharsh/grpc,makdharma/grpc,nicolasnoble/grpc,thinkerou/grpc,vsco/grpc,jtattermusch/grpc,leifurhauks/grpc,fuchsia-mirror/third_party-grpc,greasypizza/grpc,PeterFaiman/ruby-grpc-minimal,hstefan/grpc,murgatroid99/grpc,Crevil/grpc,mehrdada/grpc,ctiller/grpc,quizlet/grpc,dklempner/grpc,baylabs/grpc,royalharsh/grpc,miselin/grpc,simonkuang/grpc,pszemus/grpc,ppietrasa/grpc,a-veitch/grpc,ipylypiv/grpc,thinkerou/grpc,goldenbull/grpc,grpc/grpc,perumaalgoog/grpc,ejona86/grpc,thunderboltsid/grpc,stanley-cheung/grpc,simonkuang/grpc,chrisdunelm/grpc,7anner/grpc,PeterFaiman/ruby-grpc-minimal,yugui/grpc,jboeuf/grpc,chrisdunelm/grpc,tamihiro/grpc,daniel-j-born/grpc,msiedlarek/grpc,donnadionne/grpc,msmania/grpc,thunderboltsid/grpc,rjshade/grpc,tamihiro/grpc,PeterFaiman/ruby-grpc-minimal,carl-mastrangelo/grpc,7anner/grpc,miselin/grpc,VcamX/grpc,kpayson64/grpc,quizlet/grpc,hstefan/grpc,firebase/grpc,perumaalgoog/grpc,vsco/grpc,nicolasnoble/grpc,kumaralokgithub/grpc,baylabs/grpc,tamihiro/grpc,yongni/grpc,andrewpollock/grpc,fuchsia-mirror/third_party-grpc,wcevans/grpc,andrewpollock/grpc,leifurhauks/grpc,soltanmm-google/grpc,infinit/grpc,kskalski/grpc,kpayson64/grpc,jboeuf/grpc,jtattermusch/grpc,y-zeng/grpc,geffzhang/grpc,pszemus/grpc,dklempner/grpc,VcamX/grpc,carl-mastrangelo/grpc,kpayson64/grpc,Vizerai/grpc,podsvirov/grpc,murgatroid99/grpc,ipylypiv/grpc,vjpai/grpc,kpayson64/grpc,dgquintas/grpc,leifurhauks/grpc,y-zeng/grpc,hstefan/grpc,ppietrasa/grpc,pszemus/grpc,VcamX/grpc,ctiller/grpc,nicolasnoble/grpc,dklempner/grpc,Vizerai/grpc,thinkerou/grpc,soltanmm-google/grpc,thinkerou/grpc,muxi/grpc,kpayson64/grpc,yugui/grpc,sreecha/grpc,grani/grpc,stanley-cheung/grpc,baylabs/grpc,sreecha/grpc,thinkerou/grpc,carl-mastrangelo/grpc,ctiller/grpc,rjshade/grpc,ppietrasa/grpc,stanley-cheung/grpc,jcanizales/grpc,fuchsia-mirror/third_party-grpc,jtattermusch/grpc,y-zeng/grpc,mehrdada/grpc,jboeuf/grpc,pszemus/grpc,ipylypiv/grpc,jcanizales/grpc,yugui/grpc,daniel-j-born/grpc,hstefan/grpc,podsvirov/grpc,ananthonline/grpc,deepaklukose/grpc,carl-mastrangelo/grpc,leifurhauks/grpc,jtattermusch/grpc,jcanizales/grpc,Crevil/grpc,muxi/grpc,dklempner/grpc,podsvirov/grpc,adelez/grpc,LuminateWireless/grpc,Vizerai/grpc,grani/grpc,apolcyn/grpc,quizlet/grpc,firebase/grpc,rjshade/grpc,bogdandrutu/grpc,Vizerai/grpc,geffzhang/grpc,yang-g/grpc,vsco/grpc,ejona86/grpc,ncteisen/grpc,pmarks-net/grpc,philcleveland/grpc,simonkuang/grpc,jtattermusch/grpc,geffzhang/grpc,nicolasnoble/grpc,baylabs/grpc,chrisdunelm/grpc,firebase/grpc,dgquintas/grpc,baylabs/grpc,yugui/grpc,murgatroid99/grpc,nicolasnoble/grpc,quizlet/grpc,pszemus/grpc,yongni/grpc,tengyifei/grpc,grpc/grpc,arkmaxim/grpc,chrisdunelm/grpc,baylabs/grpc,a11r/grpc,kriswuollett/grpc,thunderboltsid/grpc,a-veitch/grpc,MakMukhi/grpc,goldenbull/grpc,stanley-cheung/grpc,podsvirov/grpc,yugui/grpc,donnadionne/grpc,pmarks-net/grpc,ppietrasa/grpc,ananthonline/grpc,simonkuang/grpc,ipylypiv/grpc,baylabs/grpc,Crevil/grpc,donnadionne/grpc,7anner/grpc,LuminateWireless/grpc,makdharma/grpc,yongni/grpc,muxi/grpc,malexzx/grpc,grpc/grpc,goldenbull/grpc,kskalski/grpc,chrisdunelm/grpc,thinkerou/grpc,zhimingxie/grpc,yang-g/grpc,soltanmm-google/grpc,dklempner/grpc,vsco/grpc,a-veitch/grpc,yongni/grpc,ejona86/grpc,a-veitch/grpc,infinit/grpc,a-veitch/grpc,pszemus/grpc,pszemus/grpc,dgquintas/grpc,apolcyn/grpc,dgquintas/grpc,bogdandrutu/grpc,chrisdunelm/grpc,pszemus/grpc,grani/grpc,philcleveland/grpc,ananthonline/grpc,kumaralokgithub/grpc,ejona86/grpc,greasypizza/grpc,Crevil/grpc,bogdandrutu/grpc,donnadionne/grpc,perumaalgoog/grpc,kumaralokgithub/grpc,ncteisen/grpc,donnadionne/grpc,wcevans/grpc,kpayson64/grpc,firebase/grpc,muxi/grpc,podsvirov/grpc,ctiller/grpc,Vizerai/grpc,arkmaxim/grpc,yongni/grpc,kskalski/grpc,apolcyn/grpc,mehrdada/grpc,rjshade/grpc,deepaklukose/grpc,yang-g/grpc,simonkuang/grpc,makdharma/grpc,zhimingxie/grpc,geffzhang/grpc,hstefan/grpc,ctiller/grpc,pszemus/grpc,malexzx/grpc,donnadionne/grpc,ctiller/grpc,stanley-cheung/grpc,greasypizza/grpc,MakMukhi/grpc,ejona86/grpc,adelez/grpc,jcanizales/grpc,pszemus/grpc,philcleveland/grpc,kriswuollett/grpc,andrewpollock/grpc,thunderboltsid/grpc,soltanmm/grpc,Vizerai/grpc,thunderboltsid/grpc,yang-g/grpc,ejona86/grpc,kpayson64/grpc,a11r/grpc,firebase/grpc,PeterFaiman/ruby-grpc-minimal,donnadionne/grpc,arkmaxim/grpc,tamihiro/grpc,MakMukhi/grpc,ctiller/grpc,royalharsh/grpc,infinit/grpc,pmarks-net/grpc,goldenbull/grpc,jboeuf/grpc,VcamX/grpc,mehrdada/grpc,jcanizales/grpc,zhimingxie/grpc,yongni/grpc,royalharsh/grpc,Vizerai/grpc,ncteisen/grpc,greasypizza/grpc,rjshade/grpc,wcevans/grpc,yugui/grpc,dgquintas/grpc,perumaalgoog/grpc,firebase/grpc,stanley-cheung/grpc,7anner/grpc,deepaklukose/grpc,tamihiro/grpc,vjpai/grpc,malexzx/grpc,kumaralokgithub/grpc,philcleveland/grpc,adelez/grpc,geffzhang/grpc,soltanmm-google/grpc,podsvirov/grpc,matt-kwong/grpc,malexzx/grpc,geffzhang/grpc,rjshade/grpc,perumaalgoog/grpc,greasypizza/grpc,miselin/grpc,thinkerou/grpc,mehrdada/grpc,infinit/grpc,MakMukhi/grpc,simonkuang/grpc,7anner/grpc,ananthonline/grpc,kpayson64/grpc,quizlet/grpc,donnadionne/grpc,fuchsia-mirror/third_party-grpc,y-zeng/grpc,andrewpollock/grpc,a11r/grpc,7anner/grpc,7anner/grpc,matt-kwong/grpc,adelez/grpc,geffzhang/grpc,infinit/grpc,makdharma/grpc,yang-g/grpc,LuminateWireless/grpc,daniel-j-born/grpc,miselin/grpc,adelez/grpc,perumaalgoog/grpc,muxi/grpc,VcamX/grpc,matt-kwong/grpc,Crevil/grpc,kskalski/grpc,greasypizza/grpc,yang-g/grpc,thunderboltsid/grpc,LuminateWireless/grpc,miselin/grpc,daniel-j-born/grpc,LuminateWireless/grpc,chrisdunelm/grpc,arkmaxim/grpc,muxi/grpc,LuminateWireless/grpc,vjpai/grpc,vsco/grpc,stanley-cheung/grpc,podsvirov/grpc,ipylypiv/grpc,kriswuollett/grpc,murgatroid99/grpc,soltanmm/grpc,msiedlarek/grpc,goldenbull/grpc,ejona86/grpc,tamihiro/grpc,vsco/grpc,perumaalgoog/grpc,ipylypiv/grpc,royalharsh/grpc,tengyifei/grpc,perumaalgoog/grpc,dklempner/grpc,simonkuang/grpc,jtattermusch/grpc,tengyifei/grpc,pmarks-net/grpc,infinit/grpc,soltanmm/grpc,apolcyn/grpc,a-veitch/grpc,mehrdada/grpc,a-veitch/grpc,ppietrasa/grpc,infinit/grpc,chrisdunelm/grpc,7anner/grpc,malexzx/grpc,grpc/grpc,jtattermusch/grpc,arkmaxim/grpc,kskalski/grpc,pmarks-net/grpc,makdharma/grpc,carl-mastrangelo/grpc,dgquintas/grpc,pmarks-net/grpc,fuchsia-mirror/third_party-grpc,zhimingxie/grpc,tengyifei/grpc,jboeuf/grpc,zhimingxie/grpc,vsco/grpc,yugui/grpc,ncteisen/grpc,vjpai/grpc,ananthonline/grpc,muxi/grpc,msmania/grpc,jboeuf/grpc,dklempner/grpc,VcamX/grpc,mehrdada/grpc,miselin/grpc,hstefan/grpc,dgquintas/grpc,vjpai/grpc,infinit/grpc,MakMukhi/grpc,donnadionne/grpc,soltanmm-google/grpc,ipylypiv/grpc,geffzhang/grpc,msiedlarek/grpc,wcevans/grpc,carl-mastrangelo/grpc,stanley-cheung/grpc,ananthonline/grpc,adelez/grpc,y-zeng/grpc,nicolasnoble/grpc,Vizerai/grpc,jcanizales/grpc,ctiller/grpc,a-veitch/grpc,malexzx/grpc,mehrdada/grpc,murgatroid99/grpc,msiedlarek/grpc,muxi/grpc,miselin/grpc,bogdandrutu/grpc,Vizerai/grpc,daniel-j-born/grpc,kskalski/grpc,matt-kwong/grpc,jcanizales/grpc,tamihiro/grpc,rjshade/grpc,royalharsh/grpc,bogdandrutu/grpc,kpayson64/grpc,ejona86/grpc,apolcyn/grpc,MakMukhi/grpc,dklempner/grpc,zhimingxie/grpc,leifurhauks/grpc,apolcyn/grpc,daniel-j-born/grpc,adelez/grpc,malexzx/grpc,sreecha/grpc,fuchsia-mirror/third_party-grpc,dgquintas/grpc,sreecha/grpc,kriswuollett/grpc,MakMukhi/grpc,grani/grpc,soltanmm-google/grpc,msiedlarek/grpc,Crevil/grpc,yongni/grpc,ctiller/grpc,soltanmm/grpc,vjpai/grpc,donnadionne/grpc,philcleveland/grpc,kriswuollett/grpc,rjshade/grpc,murgatroid99/grpc,sreecha/grpc,msmania/grpc,carl-mastrangelo/grpc,greasypizza/grpc,adelez/grpc,simonkuang/grpc,muxi/grpc,tengyifei/grpc,mehrdada/grpc,infinit/grpc,soltanmm/grpc,perumaalgoog/grpc,mehrdada/grpc,a11r/grpc,sreecha/grpc,vjpai/grpc,ppietrasa/grpc,msmania/grpc,soltanmm-google/grpc,yugui/grpc,VcamX/grpc,a11r/grpc,chrisdunelm/grpc,makdharma/grpc,msmania/grpc,kskalski/grpc,soltanmm-google/grpc,vjpai/grpc,royalharsh/grpc,firebase/grpc,VcamX/grpc,leifurhauks/grpc,Crevil/grpc,philcleveland/grpc,donnadionne/grpc,kumaralokgithub/grpc,ncteisen/grpc,kskalski/grpc,matt-kwong/grpc,kumaralokgithub/grpc,ncteisen/grpc,jboeuf/grpc,mehrdada/grpc,ejona86/grpc,goldenbull/grpc,jboeuf/grpc,fuchsia-mirror/third_party-grpc,PeterFaiman/ruby-grpc-minimal,soltanmm/grpc,LuminateWireless/grpc,kriswuollett/grpc,simonkuang/grpc,nicolasnoble/grpc,royalharsh/grpc,makdharma/grpc,apolcyn/grpc,goldenbull/grpc,rjshade/grpc,podsvirov/grpc,quizlet/grpc,matt-kwong/grpc,ananthonline/grpc,grpc/grpc,y-zeng/grpc,murgatroid99/grpc,ctiller/grpc,deepaklukose/grpc,a11r/grpc,yang-g/grpc,pszemus/grpc,carl-mastrangelo/grpc,LuminateWireless/grpc,quizlet/grpc,jtattermusch/grpc,ctiller/grpc,vjpai/grpc,deepaklukose/grpc,thinkerou/grpc,thinkerou/grpc,VcamX/grpc,baylabs/grpc,ananthonline/grpc,grani/grpc,fuchsia-mirror/third_party-grpc,deepaklukose/grpc,ppietrasa/grpc,jboeuf/grpc,Vizerai/grpc,grpc/grpc,goldenbull/grpc,firebase/grpc,ejona86/grpc,vjpai/grpc,goldenbull/grpc,makdharma/grpc,ppietrasa/grpc,PeterFaiman/ruby-grpc-minimal,nicolasnoble/grpc,chrisdunelm/grpc