Update third_party/protobuf to protobuf-v3.0.0-beta-3

third_party/protobuf/csharp/src/Google.Protobuf.JsonDump/Program.cs

 #region Copyright notice and license
 // Protocol Buffers - Google's data interchange format
 // Copyright 2008 Google Inc.  All rights reserved.
 // https://developers.google.com/protocol-buffers/
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
@@ skipping 52 matching lines @@
             IMessage message = (IMessage) Activator.CreateInstance(type);
             using (var input = File.OpenRead(args[1]))
             {
                 message.MergeFrom(input);
             }
             Console.WriteLine(message);
             return 0;
         }
     }
 }