Make new Proc::Async constructor friendly to subclass attribs.
Make new Proc::Async constructor friendly to subclass attribs.

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