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

frog/minfrogc.dart

Index: frog/minfrogc.dart
diff --git a/frog/minfrogc.dart b/frog/minfrogc.dart
index 39c4f2691d676e88100625e77a6a6144c219592d..5b9a83c047ffa7852a18751810e19f5e3bb7d89f 100644
--- a/frog/minfrogc.dart
+++ b/frog/minfrogc.dart
@@ -1,9 +1,10 @@
-// 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.
 
 #library('minfrogc');
 
+#import('dart:io');
 #import('file_system_vm.dart');
 #import('lang.dart');