changed IMap to an interface (fixed issue #1629)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6441 f16182fa-f095-11de-8f43-4547254af6c6
didn't mean to commit that

git-svn-id: http://haxe.googlecode.com/svn/trunk@6442 f16182fa-f095-11de-8f43-4547254af6c6