Parameter.$!nominal_type is always bound
Parameter.$!nominal_type is always bound

So no need for decont()ing.  Also add some comments to make sense of the
bitmap values.

salortiz/rakudo,rakudo/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,tony-o/rakudo,tbrowder/rakudo,labster/rakudo,Gnouc/rakudo,softmoth/rakudo,softmoth/rakudo,labster/rakudo,rakudo/rakudo,salortiz/rakudo,nbrown/rakudo,salortiz/rakudo,tony-o/rakudo,softmoth/rakudo,MasterDuke17/rakudo,softmoth/rakudo,labster/rakudo,tony-o/rakudo,MasterDuke17/rakudo,rakudo/rakudo,nbrown/rakudo,salortiz/rakudo,salortiz/rakudo,tony-o/rakudo,Gnouc/rakudo,tbrowder/rakudo,Gnouc/rakudo,nbrown/rakudo,rakudo/rakudo,tony-o/rakudo,tbrowder/rakudo,labster/rakudo,softmoth/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,Gnouc/rakudo,MasterDuke17/rakudo,rakudo/rakudo,labster/rakudo,Gnouc/rakudo,tony-o/rakudo,salortiz/rakudo,nbrown/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,rakudo/rakudo,tbrowder/rakudo,nbrown/rakudo,labster/rakudo,nbrown/rakudo