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

tests/standalone/src/ListOutputStreamTest.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.
 
+#import("dart:io");
+
 void testEmptyListOutputStream1() {
   OutputStream stream = new ListOutputStream();
   Expect.equals(null, stream.contents());
   stream.close();
   Expect.equals(null, stream.contents());
   Expect.throws(() { stream.write([0]); });
 }
 
 
 void testEmptyListOutputStream2() {
@@ skipping 66 matching lines @@
 
   donePort.receive((x,y) => donePort.close());
 }
 
 main() {
   testEmptyListOutputStream1();
   testEmptyListOutputStream2();
   testListOutputStream1();
   testListOutputStream2();
 }