Eliminate old style import from language tests

tests/language/prefix10_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("Prefix10Test.dart");
-#import("library10.dart", prefix : "lib10");
-#import("library11.dart", prefix : "lib11");
+library Prefix10Test.dart;
+import "library10.dart" as lib10;
+import "library11.dart" as lib11;
 
 class Prefix10Test {
   static Test1() {
     var result = 0;
     var obj = new lib10.Library10(1);
     result = obj.fld;
     Expect.equals(1, result);
     result += obj.func();
     Expect.equals(3, result);
     result += lib10.Library10.static_func();
@@ skipping 22 matching lines @@
     Expect.equals(200, lib11.top_level_func11());
   }
 }
 
 main() {
   Prefix10Test.Test1();
   Prefix10Test.Test2();
   Prefix10Test.Test3();
   Prefix10Test.Test4();
 }