Implement import scope

tests/language/library5_negative_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.
-
-// This tests that it is a compile-time error to import two libraries that
-// both define a function type alias with the same name.
-// This name conflict is considered an error even if Fun is never referred to.
-
-#library("Library5NegativeTest.dart");
-#import("library5a.dart");  // Defines function type alias Fun
-#import("library5b.dart");  // Also defines function type alias Fun
-
-main() {
-}