Enable constructor name check by default

tests/language/named_constructor_test.dart

-// 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.
-
-class NamedConstructorTest {
-  int x_;
-
-  NamedConstructorTest.fill(int x) {
-    // Should resolve to the fill method
-    fill(x);
-  }
-
-  void fill(int x) {
-    x_ = x;
-  }
-
-  static testMain() {
-    var a = new NamedConstructorTest.fill(3);
-    assert(a.x_ == 3);
-  }
-}
-
-main() {
-  NamedConstructorTest.testMain();
-}