Reimplement .native-descriptor for async sockets
Reimplement .native-descriptor for async sockets

This gets the file descriptor of the socket. This was originally
implemented before release 2018.10, but was reverted due to bugs.

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