[regression] Constraining class object against structure AND class throws off DCE.

[back2dos]

Minimal example (plus the closest thing that does work).

class Test {
  static function main() {
    foo1(Test);// works
    foo2(Test);// fails, because bar2 is eliminated
  }

  static public function bar1() return 'bar1';
  static public function bar2() return 'bar2';

  static function foo1<T:{ function bar1():String; }>(cl:T)
    return cl.bar1();

  static function foo2<T:Class<Dynamic> & { function bar2():String; }>(cl:T)
    return cl.bar2();
}

This broke with constrained monos (0ddd26d). The build before (1cc4752) is still working.