[python] don't generate extern enums and support @:pythonImport for extern enums (closes #3925)
[python] don't generate extern enums and support @:pythonImport for extern enums (closes #3925)

pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe,pleclech/hacking-haxe