unittest step2: bye bye to multiple entrypoints for unittest

utils/tests/pub/pub_tests.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.
 
 #library('pub_tests');
 
 #import('dart:io');
 
 #import('test_pub.dart');
-#import('../../../lib/unittest/unittest_vm.dart');
+#import('../../../lib/unittest/unittest.dart');
 
 main() {
   group('running pub with no command', () {
     testOutput('displays usage',
       [],
       '''
       Pub is a package manager for Dart.
 
       Usage:
 
@@ skipping 13 matching lines @@
 
   group('an unknown command', () {
     testOutput('displays an error message',
       ['quylthulg'],
       '''
       Unknown command "quylthulg".
       Run "pub help" to see available commands.''',
       exitCode: 64);
   });
 }