Language tests updated to use const instead of final.

tests/language/ct_const4_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.
 // Check compile-time constant library references with prefixes
 
 #library("CTConst4Test");
 #import("ct_const4_lib.dart", prefix:"mylib");
 
-final A = mylib.B;
+const A = mylib.B;
 
 main() {
   Expect.equals(1, A);
 }