anchor.diff:  % as defined in http://www.w3.org/TR/cors/#terminology
   -define(SIMPLE_HEADERS, ["Cache-Control", "Content-Language",
           "Content-Type", "Expires", "Last-Modified", "Pragma"]).
  +-define(ALLOWED_HEADERS, lists:sort(["Server", "Etag",
  +        "Accept-Ranges" | ?SIMPLE_HEADERS])).
   -define(SIMPLE_CONTENT_TYPE_VALUES, ["application/x-www-form-urlencoded",
           "multipart/form-data", "text/plain"]).
   
  
positive.code:     % return: RequestHeaders ++ CorsHeaders ++ ACEH
  
      RequestHeaders = [K || {K,_V} <- RequestHeaders0],
      ExposedHeaders0 = reduce_headers(RequestHeaders, ?SIMPLE_HEADERS),
  
      % here we may have not moved Content-Type into ExposedHeaders,
      % now we need to check whether the Content-Type valus is
  
negative.code:     reduce_headers0(A, B, []).
  
  reduce_headers0([], _B, Result) ->
      lists:sort(Result);
  reduce_headers0([ElmA|RestA], B, Result) ->
      R = case member_nocase(ElmA, B) of
      false -> Result;
      _Else -> [ElmA | Result]
      end,
      reduce_headers0(RestA, B, R).
  