Remove signature classes from the VM.

tests/language/regress_24567_test.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import "package:expect/expect.dart";
+import 'dart:math' as math;
 
-class A<T> {}
+class Random { }
 
-class C<T> {
-  a() {
-    return () => new A<T>();
-  }
-}
+typedef F(Random r);
 
 main() {
-  Expect.isTrue(new C<int>().a()() is A<int>);
-  Expect.isFalse(new C<int>().a()() is A<String>);
+  f(Random r) { }
+  g(math.Random r) { }
+  Expect.isTrue(f is F);
+  Expect.isFalse(g is F);
 }