Added extra valid request (099) and test (send_special_chunks).

``send_special_chunks`` sends the request data in two chunks, one having a length of 1 byte, which ensures there is no CRLF, and a second chunk containing the rest of the request data. Practically, this forces ``gunicorn.http.message.Request.read_line()`` to get the full request data with two buffer reads and reveal possible bugs related to the internal buffer mechanism. See #670 for more information.