(fixed issue #1691)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6449 f16182fa-f095-11de-8f43-4547254af6c6
do not allow WeakMap being assigned to Map (fixed issue #1688)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6450 f16182fa-f095-11de-8f43-4547254af6c6