Introduces the new syntax for deferred loading

tests/language/deferred_shadow_load_library_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';
+
+// This library contains a member loadLibrary.
+// Check that we shadow this member.
+import "deferred_shadow_load_library_lib.dart" deferred as lib;
+
+void main() {
+  var x = lib.loadLibrary();
+  Expect.isTrue(x is Future);
+  asyncStart();
+  x.then((_) {
+    Expect.isTrue(lib.trueVar);
+    // Check that shadowing still is in place after loading the library.
+    Expect.isTrue(lib.loadLibrary() is Future);
+    asyncEnd();
+  });
+}