Language tests updated to use const instead of final.

tests/language/library_prefixes_test2.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.
 
 class Constants {
-  static final PI = 3.14;
-  static final foo = 2;
+  static const PI = 3.14;
+  static const foo = 2;
 }
 
 class A {
-  static final y = 0;
+  static const y = 0;
   int x;
   A() : x = 2 {}
   A.named() : x = 4 {}
   A.superC(x) : x = x + 11 {}
   factory A.fac() { return new A.named(); }
 }
 
 class B extends A {
   B() : super() {}
   B.named() : super.superC(2) {}
@@ skipping 16 matching lines @@
 
 class E {
   var f;
   E() {}
   E.fun(x) : f = (() { return x + 13; }) {}
   static foo() { return 3; }
   static fooo(x) { return () { return x + 1024; }; }
   bar() { return 4; }
   toto(x) { return () { return x + 5; }; }
 }