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

tests/standalone/src/DirectoryTest.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.
 //
 // Directory listing test.
 
+#import("dart:io");
+
 class DirectoryTest {
   static void testListing() {
     bool listedDir = false;
     bool listedFile = false;
 
     Directory directory = new Directory("");
     directory.createTempSync();
     Directory subDirectory = new Directory("${directory.path}/subdir");
     Expect.isFalse(subDirectory.existsSync());
     subDirectory.createSync();
@@ skipping 280 matching lines @@
   dir.createTemp();
 }
 
 
 main() {
   DirectoryTest.testMain();
   NestedTempDirectoryTest.testMain();
   testCreateTempErrorSync();
   testCreateTempError();
 }