Add support for the node net module.

frog/lib/node/util.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.
+
+#library('util.dart');
+#import('node.dart');
+
+typedef void UtilPumpCallback(Error error);
+
+class util native "require('util')" {
+  static void debug(String string) native;
+  static void log(String string) native;
+  static void inspect(var object, [bool showHidden=false, num depth=2,
+    bool colors=false]) native;
+  static bool isArray(var object) native;
+  static bool isRegExp(var object) native;
+  static bool isDate(var object) native;
+  static bool isError(var object) native;
+  static pump(ReadableStream readableStream, WritableStream writeableStream,
+    [UtilPumpCallback callback]) native;
+  // the method inherits(a,b) doesn't make sense for Dart
+}