Revert "Switch libraries to using new tags."

sdk/lib/io/stdio.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_io;
-
 const int _STDIO_HANDLE_TYPE_TERMINAL = 0;
 const int _STDIO_HANDLE_TYPE_PIPE = 1;
 const int _STDIO_HANDLE_TYPE_FILE = 2;
 const int _STDIO_HANDLE_TYPE_SOCKET = 3;
 const int _STDIO_HANDLE_TYPE_OTHER = -1;
 
 
 InputStream _stdin;
 OutputStream _stdout;
 OutputStream _stderr;
@@ skipping 55 matching lines @@
     _stderr = _getStdioOutputStream(2);
   }
   return _stderr;
 }
 
 
 class _StdIOUtils {
   external static _getStdioHandle(Socket socket, int num);
   external static _getStdioHandleType(int num);
 }