Fixed tests so they do indeed confirm that values on optional named parameters are not allowed. Add…

tests/language/named_parameters_negative_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 testing named parameters.
-
-
-class NamedParametersNegativeTest {
-
-  static int F31(int a, [int b = 20, int c = 30]) {
-    return 100*(100*a + b) + c;
-  }
-
-  static testMain() {
-    F31(b:25, c:35);  // No positional argument passed.
-  }
-}
-
-main() {
-  NamedParametersNegativeTest.testMain();
-}