Eliminate old style import from language tests

tests/language/prefix22_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.
 //
 // Unresolved symbols should be reported as static type warnings.
 // This should not prevent execution.
 
-#library("Prefix21NegativeTest.dart");
-#import("library12.dart", prefix:"lib12");
+library Prefix21NegativeTest.dart;
+import "library12.dart" as lib12;
 
 class myClass {
   myClass(lib12.Library13 p) {  /// static type warning
   }
 }
 
 main() {
   new myClass(null);  // no dynamic type error when assigning null
 }