Move core and coreimpl from corelib/ to lib/core and lib/coreimpl.

corelib/src/int.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.
-
-// Dart core library.
-
-interface int extends num {
-  // Bit-operations.
-  int operator &(int other);
-  int operator |(int other);
-  int operator ^(int other);
-  int operator ~();
-  int operator <<(int shiftAmount);
-  int operator >>(int shiftAmount);
-
-  // Testers.
-  bool isEven();
-  bool isOdd();
-
-  // Specializations of super-interface.
-  int operator negate();
-  int abs();
-  int round();
-  int floor();
-  int ceil();
-  int truncate();
-}