Move unittest from lib to pkg.

tests/html/svgelement2_test.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('SVGElement2Test');
-#import('../../lib/unittest/unittest.dart');
-#import('../../lib/unittest/html_config.dart');
+#import('../../pkg/unittest/unittest.dart');
+#import('../../pkg/unittest/html_config.dart');
 #import('dart:html');
 #import('svgelement_test.dart', prefix: 'originalTest');
 
 class A {
   var _this;
   A(x) : this._this = x;
 }
 
 main() {
   // The svgelement_test requires the field "_this" to map to "_this". In this
   // test-case we use another library's '_this' first (see issue 3039 and
   // _ChildNodeListLazy.first).
   Expect.equals(499, new A(499)._this);
   originalTest.main();
 }