Extend the mDNS package with a native extension used on Mac OS

pkg/mdns/test/decode_test.dart

-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2015, the Fletch 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.
+// BSD-style license that can be found in the LICENSE.md file.
 
 import 'package:expect/expect.dart';
 import 'package:mdns/src/packet.dart';
 
 main() {
   testValidPackages();
   testBadPackages();
   testHexDumpList();
 }
 
@@ skipping 93 matching lines @@
     if (x.length == 1) s += '0';
     s += x;
     if (((i + 1) % 8) == 0) {
       s += ',';
       print(s);
       s = '';
     }
   }
   if (s.length != 0) print(s);
 }
-