Optimize away ref taking when args are known ro.
Optimize away ref taking when args are known ro.

This only works for subs, and then only those we can compile-time
analyze. Still, that covers quite a lot of ground for code using
native types.

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