unfork DDC's copy of most SDK libraries

pkg/dev_compiler/tool/input_sdk/lib/io/eventhandler.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;
-
-class _EventHandler {
-  external static void _sendData(Object sender,
-                                 SendPort sendPort,
-                                 int data);
-}