remove haxe.ds.Either
Support type hints in @:enum abstract fields (to support GADT-like behaviour)
Merge pull request #3493 from nadako/enum_abstract_gadt

Support type hints in @:enum abstract fields (to support GADT-like behaviour)
allow extending extern base classes by extern classes
[js] add js.RegExp extern
[js] use js.RegExp instead of Dynamic in EReg