naive: fix malformed http 1.0 request

[Chilledheart]

HttpRequestHeaders::ToString not only has CRLR for every header, but also has the trailing CRLR.

It might affect POST/PUT methods.

  // Serializes HttpRequestHeaders to a string representation.  Joins all the
  // header keys and values with ": ", and inserts "\r\n" between each header
  // line, and adds the trailing "\r\n".
  std::string ToString() const;

[klzgrad]

Separately fixed in master.