Update unittest to new package layout.

tests/isolate/isolate_complex_messages_test.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.
 
 // Dart test program for testing isolate communication with
 // complex messages.
 
 #library('IsolateComplexMessagesTest');
 #import('dart:isolate');
-#import('../../pkg/unittest/unittest.dart');
+#import('../../pkg/unittest/lib/unittest.dart');
 
 main() {
   test("complex messages are serialized correctly", () {
     SendPort remote = spawnFunction(logMessages);
     remote.send(1, null);
     remote.send("Hello", null);
     remote.send("World", null);
     remote.send(const [null, 1, 2, 3, 4], null);
     remote.send(const [1, 2.0, true, false, 0xffffffffff], null);
     remote.send(const ["Hello", "World", 0xffffffffff], null);
@@ skipping 43 matching lines @@
           Expect.equals(3, message.length);
           Expect.equals("Hello", message[0]);
           Expect.equals("World", message[1]);
           Expect.equals(0xffffffffff, message[2]);
           break;
       }
       count++;
     }
   });
 }