isolates refactor: this change introduces 'dart:isolate' as a library. This is a

tests/isolate/src/CrossIsolateMessageTest.dart

 // Copyright (c) 2011, 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.
 
 // Dart test program for testing that isolates can communicate to isolates
 // other than the main isolate.
 
 #library('CrossIsolateMessageTest');
+#import('dart:isolate');
 #import('TestFramework.dart');
 
 class CrossIsolate1 extends Isolate {
   CrossIsolate1() : super.heavy();
 
   void main() {
     this.port.receive((msg, replyTo) {
       SendPort otherIsolate = msg;
       ReceivePort receivePort = new ReceivePort();
       receivePort.receive((msg, replyTo) {
@@ skipping 44 matching lines @@
           port1b.send(42, null);
         }));
       }));
     });
   });
 }
 
 main() {
   runTests([test]);
 }