Support const modifier in fields, variables

tests/language/const_syntax_test.dart

Index: tests/language/const_syntax_test.dart
===================================================================
--- tests/language/const_syntax_test.dart	(revision 9982)
+++ tests/language/const_syntax_test.dart	(working copy)
@@ -1,18 +0,0 @@
-// Copyright (c) 2011, 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.
-
-main() {
-  Expect.equals(42, FOO);   /// 01: compile-time error
-  Expect.equals(87, BAR);   /// 02: compile-time error
-  Expect.equals(42, C.FOO); /// 03: compile-time error
-  Expect.equals(87, C.FOO); /// 04: compile-time error
-}
-
-const FOO = 42;     /// 01: continued
-const int BAR = 87; /// 02: continued
-
-class C {
-  static const FOO = 42;     /// 03: continued
-  static const int BAR = 87; /// 04: continued
-}