Improvements to 53-bit overflow checking.

tests/standalone/53bit_overflow_literal_test.dart

+// Copyright (c) 2013, 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.
+
+// VMOptions=--throw_on_javascript_int_overflow
+
+
+import "package:expect/expect.dart";
+
+int literals() {
+  var okay_literal = 0xFFFFFFFFFFFFF;
+  var too_big_literal = 0x1FFFFFFFFFFFFF;  /// 01: compile-time error
+  return okay_literal;
+}
+
+main() {
+  Expect.equals(0xFFFFFFFFFFFFF, literals());
+}