A few little optimizations to some Str builtins. Found by looking at profile of code from masak++; seems to shave a few percent off it.
A few little optimizations to some Str builtins. Found by looking at profile of code from masak++; seems to shave a few percent off it.

retupmoca/rakudo,tony-o/deb-rakudodaily,paultcochrane/rakudo,LLFourn/rakudo,zostay/rakudo,salortiz/rakudo,labster/rakudo,rakudo/rakudo,Leont/rakudo,jonathanstowe/rakudo,b2gills/rakudo,tbrowder/rakudo,Gnouc/rakudo,skids/rakudo,tony-o/rakudo,lucasbuchala/rakudo,azawawi/rakudo,salortiz/rakudo,niner/rakudo,tony-o/rakudo,tbrowder/rakudo,ab5tract/rakudo,ugexe/rakudo,tony-o/rakudo,cygx/rakudo,ab5tract/rakudo,cognominal/rakudo,usev6/rakudo,skids/rakudo,MasterDuke17/rakudo,cognominal/rakudo,tony-o/rakudo,tbrowder/rakudo,ab5tract/rakudo,Gnouc/rakudo,b2gills/rakudo,jonathanstowe/rakudo,nbrown/rakudo,MasterDuke17/rakudo,LLFourn/rakudo,dankogai/rakudo,MasterDuke17/rakudo,zostay/rakudo,paultcochrane/rakudo,nunorc/rakudo,teodozjan/rakudo,paultcochrane/rakudo,ugexe/rakudo,sjn/rakudo,nunorc/rakudo,b2gills/rakudo,retupmoca/rakudo,skids/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,zhuomingliang/rakudo,ugexe/rakudo,tony-o/deb-rakudodaily,rakudo/rakudo,azawawi/rakudo,ungrim97/rakudo,rjbs/rakudo,raydiak/rakudo,laben/rakudo,cygx/rakudo,dankogai/rakudo,softmoth/rakudo,lucasbuchala/rakudo,tony-o/deb-rakudodaily,usev6/rakudo,softmoth/rakudo,ugexe/rakudo,softmoth/rakudo,nunorc/rakudo,azawawi/rakudo,raydiak/rakudo,Gnouc/rakudo,pmurias/rakudo,laben/rakudo,pmurias/rakudo,tony-o/deb-rakudodaily,awwaiid/rakudo,softmoth/rakudo,b2gills/rakudo,azawawi/rakudo,labster/rakudo,dankogai/rakudo,dankogai/rakudo,awwaiid/rakudo,dwarring/rakudo,cygx/rakudo,Gnouc/rakudo,sergot/rakudo,Leont/rakudo,paultcochrane/rakudo,lucasbuchala/rakudo,azawawi/rakudo,rakudo/rakudo,salortiz/rakudo,cygx/rakudo,paultcochrane/rakudo,LLFourn/rakudo,nbrown/rakudo,salortiz/rakudo,LLFourn/rakudo,salortiz/rakudo,pmurias/rakudo,tony-o/rakudo,sjn/rakudo,zostay/rakudo,zostay/rakudo,rakudo/rakudo,zhuomingliang/rakudo,laben/rakudo,samcv/rakudo,tony-o/deb-rakudodaily,dwarring/rakudo,labster/rakudo,retupmoca/rakudo,rakudo/rakudo,cognominal/rakudo,awwaiid/rakudo,zhuomingliang/rakudo,retupmoca/rakudo,sjn/rakudo,samcv/rakudo,tony-o/deb-rakudodaily,niner/rakudo,tbrowder/rakudo,ungrim97/rakudo,tony-o/deb-rakudodaily,zhuomingliang/rakudo,ab5tract/rakudo,tbrowder/rakudo,raydiak/rakudo,MasterDuke17/rakudo,cognominal/rakudo,nunorc/rakudo,nbrown/rakudo,b2gills/rakudo,MasterDuke17/rakudo,usev6/rakudo,raydiak/rakudo,ugexe/rakudo,samcv/rakudo,sjn/rakudo,skids/rakudo,tbrowder/rakudo,laben/rakudo,nbrown/rakudo,LLFourn/rakudo,sergot/rakudo,Leont/rakudo,sergot/rakudo,nbrown/rakudo,jonathanstowe/rakudo,awwaiid/rakudo,nbrown/rakudo,tony-o/rakudo,lucasbuchala/rakudo,skids/rakudo,labster/rakudo,teodozjan/rakudo,usev6/rakudo,ungrim97/rakudo,dwarring/rakudo,samcv/rakudo,niner/rakudo,dwarring/rakudo,salortiz/rakudo,softmoth/rakudo,niner/rakudo,cognominal/rakudo,rjbs/rakudo,lucasbuchala/rakudo,teodozjan/rakudo,cygx/rakudo,Gnouc/rakudo,rjbs/rakudo,rakudo/rakudo,sergot/rakudo,Leont/rakudo,jonathanstowe/rakudo,ungrim97/rakudo,samcv/rakudo,ungrim97/rakudo,usev6/rakudo,dankogai/rakudo,pmurias/rakudo,teodozjan/rakudo,labster/rakudo,awwaiid/rakudo,labster/rakudo,Gnouc/rakudo,sjn/rakudo,ab5tract/rakudo