Add test where X is defined differentlty in co-importing libraries

tests/language/src/LibrarySameNameUsedLib1.dart

Index: tests/language/src/LibrarySameNameUsedLib1.dart
diff --git a/tests/language/src/LibrarySameNameUsedLib1.dart b/tests/language/src/LibrarySameNameUsedLib1.dart
new file mode 100644
index 0000000000000000000000000000000000000000..85aaa7688ede682531c99da1848bcd0d3a662a16
--- /dev/null
+++ b/tests/language/src/LibrarySameNameUsedLib1.dart
@@ -0,0 +1,11 @@
+// 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('lib1');
+#import('LibrarySameNameUsedLib2.dart', prefix:'lib2');
+
+interface X {
+}
+
+X makeX() { return new lib2.X(); }