Split dart:builtin into dart:builtin and dart:io.

samples/markdown/markdown.dart

Index: samples/markdown/markdown.dart
diff --git a/samples/markdown/markdown.dart b/samples/markdown/markdown.dart
index bf1d691b2fe09239a59d31ab6d052d047736f474..9bc1e53614b65882533889fc5a661dfa30f8e85f 100644
--- a/samples/markdown/markdown.dart
+++ b/samples/markdown/markdown.dart
@@ -1,10 +1,11 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
 /// Standalone script for parsing markdown from files and converting to HTML.
 #library('markdown_app');
 
+#import('dart:io');
 #import('lib.dart');
 
 main() {