Introduces the new syntax for deferred loading

tests/language/deferred_constraints_constants_old_syntax_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.
 
 import "dart:async";
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 
-@lazy import "deferred_constraints_constants_lib.dart" as lib;
+@lazy import "deferred_constraints_constants_old_syntax_lib.dart" as lib;
 
 const lazy = const DeferredLibrary('lib');
 
 const myConst1 =
   lib.constantInstance; /// reference1: compile-time error
   /*                    /// reference1: continued
   499;
   */                    /// reference1: continued
 const myConst2 =
   lib.Const.instance; /// reference2: compile-time error
@@ skipping 34 matching lines @@
     f1();
     f2();
     var constInstance = lib.constantInstance; /// reference_after_load: ok
     var h1 = new H1();
     var h2 = new H2();
     var h3 = new H3();
     asyncEnd();
   });
 }