temporally remove structure constant flag to allow second chance unification for using fields/constraints (fixed issue #1616)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6447 f16182fa-f095-11de-8f43-4547254af6c6
improved handling of special TAnon wrt unification (fixed issue #1485)

git-svn-id: http://haxe.googlecode.com/svn/trunk@6448 f16182fa-f095-11de-8f43-4547254af6c6