Revert "Remaining private libs"

sdk/lib/core/iterator.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.
 
-part of "dart:core";
+part of "core.dart";
 
 /**
  * An interface for getting items, one at a time, from an object.
  *
  * The for-in construct transparently uses `Iterator` to test for the end
  * of the iteration, and to get each item (or _element_).
  *
  * If the object iterated over is changed during the iteration, the
  * behavior is unspecified.
  *
@@ skipping 37 matching lines @@
    * element, or if the iterator has been moved past the last element of the
    * [Iterable].
    *
    * The `current` getter should keep its value until the next call to
    * [moveNext], even if an underlying collection changes.
    * After a successful call to `moveNext`, the user doesn't need to cache
    * the current value, but can keep reading it from the iterator.
    */
   E get current;
 }