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

tests/stub-generator/test_config.dart

-// 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("stub_generator_test_config");
 
+#import("dart:io");
+
 #import("../../tools/testing/dart/test_suite.dart");
 
 class StubGeneratorTestSuite extends StandardTestSuite {
   String dartcPath;
 
   StubGeneratorTestSuite(Map configuration)
       : super(configuration,
               "stub-generator",
               "tests/stub-generator/src",
               ["tests/stub-generator/stub-generator.status"]) {
@@ skipping 123 matching lines @@
         String interfaceFile = splitIsolateStubsOptions[0];
         String classes = splitIsolateStubsOptions[1];
         generateTestCase(filename, interfaceFile, classes, (String filename) {
           createTestCase(filename, optionsFromFile['isNegative']);
           testGeneratorDone();
         });
       }
     }
   }
 }