anchor.diff:          488 -> <<"Not Acceptable Here">>;
           491 -> <<"Request Pending">>;
           493 -> <<"Undecipherable">>;
  +        494 -> <<"Security Agreement Required">>;
           500 -> <<"Server Internal Error">>;
           501 -> <<"Not Implemented">>;
           502 -> <<"Bad Gateway">>;
  
positive.code:         504 -> <<"Server Time-out">>;
          505 -> <<"Version Not Supported">>;
          513 -> <<"Message Too Large">>;
          600 -> <<"Busy Everywhere">>;
          603 -> <<"Decline">>;
          604 -> <<"Does Not Exist Anywhere">>;
          606 -> <<"Not Acceptable">>;
          _ -> <<"Unknown Code">>
      end.
  
  %% @private
  gen_opts(Opts) ->
  
negative.code:         403 -> <<"Forbidden">>;
          404 -> <<"Not Found">>;
          405 -> <<"Method Not Allowed">>;
          406 -> <<"Not Acceptable">>;
          407 -> <<"Proxy Authentication Required">>;
          408 -> <<"Request Timeout">>;
          410 -> <<"Gone">>;
          412 -> <<"Conditional Request Failed">>;
          413 -> <<"Request Entity Too Large">>;
          414 -> <<"Request-URI Too Long">>;
          415 -> <<"Unsupported Media Type">>;
          416 -> <<"Unsupported URI Scheme">>;
          417 -> <<"Unknown Resource Priority">>;
          420 -> <<"Bad Extension">>;
          421 -> <<"Extension Required">>;
          422 -> <<"Session Interval Too Small">>;
          423 -> <<"Interval Too Brief">>;
          428 -> <<"Use Identity Header">>;
          429 -> <<"Provide Referrer Identity">>;
          436 -> <<"Bad Indentity-Info">>;
          437 -> <<"Unsupported Certificate">>;
          438 -> <<"Invalid Identity Header">>;
          480 -> <<"Temporarily Unavailable">>;
          481 -> <<"Call/Transaction Does Not Exist">>;
          482 -> <<"Loop Detected">>;
  