Support for type dynamic in VM

tests/language/cast2_test.dart

 // Copyright (c) 2012, 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.
 // Dart test program for constructors and initializers.
 
 // Test 'expression as Type' casts.
 
 class C {
   final int foo = 42;
 }
 
 class D extends C {
   final int bar = 37;
 }
 
 main() {
   Object oc = new C();
   Object od = new D();
 
-  (oc as Dynamic).bar;  /// 01: runtime error
+  (oc as dynamic).bar;  /// 01: runtime error
 }