delay generic expression mapping until after all field types are updated

git-svn-id: http://haxe.googlecode.com/svn/trunk@6618 f16182fa-f095-11de-8f43-4547254af6c6
- added haxe.ds.BalancedTree
- added haxe.ds.EnumValueMap
- added Reflect.isEnumValue


git-svn-id: http://haxe.googlecode.com/svn/trunk@6619 f16182fa-f095-11de-8f43-4547254af6c6