Optimize the Buf.splice(offset,size?) case
Optimize the Buf.splice(offset,size?) case

And by consequence, also optimize the other cases

salortiz/rakudo,Gnouc/rakudo,rakudo/rakudo,samcv/rakudo,usev6/rakudo,lucasbuchala/rakudo,samcv/rakudo,tony-o/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,azawawi/rakudo,salortiz/rakudo,b2gills/rakudo,lucasbuchala/rakudo,azawawi/rakudo,tony-o/rakudo,rakudo/rakudo,salortiz/rakudo,awwaiid/rakudo,salortiz/rakudo,rakudo/rakudo,rakudo/rakudo,raydiak/rakudo,ab5tract/rakudo,b2gills/rakudo,nbrown/rakudo,MasterDuke17/rakudo,jonathanstowe/rakudo,tony-o/rakudo,raydiak/rakudo,zostay/rakudo,usev6/rakudo,softmoth/rakudo,softmoth/rakudo,jonathanstowe/rakudo,awwaiid/rakudo,awwaiid/rakudo,zostay/rakudo,samcv/rakudo,azawawi/rakudo,softmoth/rakudo,labster/rakudo,nbrown/rakudo,sjn/rakudo,usev6/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,ab5tract/rakudo,salortiz/rakudo,rakudo/rakudo,softmoth/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,ab5tract/rakudo,lucasbuchala/rakudo,awwaiid/rakudo,raydiak/rakudo,Gnouc/rakudo,labster/rakudo,usev6/rakudo,labster/rakudo,tony-o/rakudo,labster/rakudo,labster/rakudo,ab5tract/rakudo,zostay/rakudo,azawawi/rakudo,sjn/rakudo,sjn/rakudo,nbrown/rakudo,rakudo/rakudo,sjn/rakudo,nbrown/rakudo,zostay/rakudo,Gnouc/rakudo,nbrown/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,ab5tract/rakudo,MasterDuke17/rakudo,sjn/rakudo,samcv/rakudo,Gnouc/rakudo,tbrowder/rakudo,lucasbuchala/rakudo,salortiz/rakudo,nbrown/rakudo,Gnouc/rakudo,tbrowder/rakudo,usev6/rakudo,tony-o/rakudo,samcv/rakudo,b2gills/rakudo,raydiak/rakudo,labster/rakudo,tbrowder/rakudo,tony-o/rakudo,b2gills/rakudo,jonathanstowe/rakudo,jonathanstowe/rakudo,azawawi/rakudo,MasterDuke17/rakudo,b2gills/rakudo,softmoth/rakudo,tbrowder/rakudo,awwaiid/rakudo