changed ObjectMap to a class

git-svn-id: http://haxe.googlecode.com/svn/trunk@6068 f16182fa-f095-11de-8f43-4547254af6c6
added serialization support for ObjectMap

git-svn-id: http://haxe.googlecode.com/svn/trunk@6069 f16182fa-f095-11de-8f43-4547254af6c6