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

tests/isolate/src/APIv2_unresolvedPortsStandaloneTest.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.
 
 // spawns multiple isolates and sends unresolved ports between them.
 #library('unresolved_ports');
+#import('dart:isolate');
 
 // This test does the following:
 //  - main spawns two isolates: 'tim' and 'beth'
 //  - 'tim' spawns an isolate: 'bob'
 //  - main starts a message chain:
 //       main -> beth -> tim -> bob -> main
 //    by giving 'beth' a send-port to 'tim'.
 
 bethIsolate(ReceivePort port) {
   port.receive((msg, reply) => msg[1].send(
@@ skipping 23 matching lines @@
 
   Isolate2 tim = new Isolate2.fromCode(timIsolate);
   Isolate2 beth = new Isolate2.fromCode(bethIsolate);
 
   beth.sendPort.send(
       // because tim is created asynchronously, here we are sending an
       // unresolved port:
       ["main says: Beth, find out if Tim is coming.", tim.sendPort],
       port.toSendPort());
 }