Fix null.runtimeType, reflect(null).type.superinterfaces, and reflect(null).getField.

tests/language/null2_test.dart

+// Copyright (c) 2014, 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.
+// Second dart test program.
+
+import "package:expect/expect.dart";
+
+// Magic incantation to avoid the compiler recognizing the constant values
+// at compile time. If the result is computed at compile time, the dynamic code
+// will not be tested.
+confuse(x) {
+  try { throw [x]; } on dynamic catch (e) { return e[0]; }

[karlklose, 2014/02/13 08:20:08]

This may break when the compiler gets smarter. I would prefer
  return new DateTime.now().millisecondsSinceEpoch == 42 ? 42 : null.

[floitsch, 2014/02/13 10:26:30]

Merged yours and the original confuse method. (also in null_test.dart where I
copied this method from).

+  return 42;
+}
+
+main() {
+  Expect.equals("Null", null.runtimeType.toString());
+  Expect.equals("Null", confuse(null).runtimeType.toString());
+}