third_party/protobuf: Update to HEAD (83d681ee2c)

third_party/protobuf/csharp/src/AddressBook/AddPerson.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 112 matching lines @@
 
             // Write the new address book back to disk.
             using (Stream output = File.OpenWrite(args[0]))
             {
                 addressBook.WriteTo(output);
             }
             return 0;
         }
     }
 }