Add an STD role.
Add an STD role.

While we inherit a bunch of stuff from HLL::Grammar, STD has a few
things factored out that we'd also like to share between languages.
They shall go into this role.

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