Do not cast scalars

git-svn-id: http://haxe.googlecode.com/svn/trunk@5982 f16182fa-f095-11de-8f43-4547254af6c6
disallow implicit to-casts if the this type is not fully known yet

git-svn-id: http://haxe.googlecode.com/svn/trunk@5983 f16182fa-f095-11de-8f43-4547254af6c6