Revert "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 {
-    if (new DateTime.now().millisecondsSinceEpoch == 42) x = 42;
-    throw [x];
-  } on dynamic catch (e) { return e[0]; }
-  return 42;
-}
-
-main() {
-  Expect.equals("Null", null.runtimeType.toString());
-  Expect.equals("Null", confuse(null).runtimeType.toString());
-}