Update pub to use new import syntax.

utils/pub/source.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('source');
+library source;
 
-#import('io.dart');
-#import('package.dart');
-#import('pubspec.dart');
-#import('system_cache.dart');
-#import('version.dart');
+import 'io.dart';
+import 'package.dart';
+import 'pubspec.dart';
+import 'system_cache.dart';
+import 'version.dart';
 
 /**
  * A source from which to install packages.
  *
  * Each source has many packages that it looks up using [PackageId]s. The source
  * is responsible for installing these packages to the package cache.
  */
 abstract class Source {
   /**
    * The name of the source. Should be lower-case, suitable for use in a
@@ skipping 161 matching lines @@
    *
    * The returned [PackageId] may have a description field that's invalid
    * according to [validateDescription], although it must still be serializable
    * to JSON and YAML. It must also be equal to [id] according to
    * [descriptionsEqual].
    *
    * By default, this just returns [id].
    */
   Future<PackageId> resolveId(PackageId id) => new Future.immediate(id);
 }