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

tests/isolate/src/Isolate2NegativeTest.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 exceptions in other isolates bring down
 // the program.
 
 #library('Isolate2NegativeTest');
+#import('dart:isolate');
 #import('TestFramework.dart');
 
 class Isolate2NegativeTest extends Isolate {
   Isolate2NegativeTest() : super();
 
   void main() {
     throw "foo";
   }
 }
 
 void test(TestExpectation expect) {
   // We will never call 'expect.succeeded'. This test fails with a timeout.
   expect.completes(new Isolate2NegativeTest().spawn());
 }
 
 main() {
   runTests([test]);
 }