Update pub to use new import syntax.

utils/pub/pubspec.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('pubspec');
+library pubspec;
 
-#import('package.dart');
-#import('source.dart');
-#import('source_registry.dart');
-#import('utils.dart');
-#import('version.dart');
-#import('yaml/yaml.dart');
+import 'package.dart';
+import 'source.dart';
+import 'source_registry.dart';
+import 'utils.dart';
+import 'version.dart';
+import 'yaml/yaml.dart';
 
 /**
  * The parsed and validated contents of a pubspec file.
  */
 class Pubspec {
   /**
    * This package's name.
    */
   final String name;
 
@@ skipping 88 matching lines @@
         source.validateDescription(description, fromLockFile: false);
 
         dependencies.add(new PackageRef(
             name, source, versionConstraint, description));
       });
     }
 
     return new Pubspec(name, version, dependencies);
   }
 }