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

tests/isolate/src/RequestReplyTest.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.
 
 #library("RequestReplyTest");
+#import("dart:isolate");
 #import("TestFramework.dart");
 
 class TestIsolate extends Isolate {
 
   TestIsolate() : super();
 
   void main() {
     this.port.receive((message, SendPort replyTo) {
       replyTo.send(message + 87);
       this.port.close();
@@ skipping 30 matching lines @@
     reply.receive(expect.runs2((message, replyTo) {
       Expect.equals(99 + 87, message);
       expect.succeeded();
     }));
   });
 }
 
 void main() {
   runTests([testCall, testSend, testSendSingleShot]);
 }