Eliminate old style import from language tests

tests/language/prefix6_negative_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.
 //
 
-#library("Prefix6NegativeTest.dart");
-#import("library10.dart", prefix:"lib10");
+library Prefix6NegativeTest.dart;
+import "library10.dart" as lib10;
 
 class Prefix6NegativeTest {
   static Test1() {
     // Variables in the local scope hide the library prefix.
     var lib10 = 0;
     var result = 0;
     result += lib10.Library10.static_func();  // This should fail.
   }
 }
 
 main() {
   Prefix6NegativeTest.Test1();
 }