Update or delete language tests using obsolete interfaces or default factory

tests/language/library_same_name_used_lib1.dart

Index: tests/language/library_same_name_used_lib1.dart
===================================================================
--- tests/language/library_same_name_used_lib1.dart	(revision 15648)
+++ tests/language/library_same_name_used_lib1.dart	(working copy)
@@ -1,11 +1,11 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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 lib1;
 import 'library_same_name_used_lib2.dart' as lib2;
 
-interface X {
+abstract class X {
 }
 
 X makeX() { return new lib2.X(); }