Commit Martin's patch for pub + lib_v2.

utils/pub/command_version.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.
 
 library command_version;
 
+import 'dart:async';
 import 'pub.dart';
 
 /// Handles the `version` pub command. 
 class VersionCommand extends PubCommand {
   String get description => 'Print pub version.';
   String get usage => 'pub version';
   bool get requiresEntrypoint => false;
 
   Future onRun() {
     printVersion();
   }
 }