test rename overhaul: step 8 - language tests

tests/language/library_private_in_constructor_b.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.
 
 #library('LibraryPrivateInConstructorB');
-#import("LibraryPrivateInConstructorA.dart");
+#import("library_private_in_constructor_a.dart");
 
 class PrivateB {
   const PrivateB();
   final _val = 42;
 }
 
 var fooB = const PrivateB();
 
 class B extends A {
   var y;
   B() : this.y = fooB._val;
 }