libcurl RTSP `CURLOPT_CRLF` conversion allows a request body to become a second RTSP request

AI WAS USED IN THE PROCESS OF IDENTIFYING THIS VULNERABILITY. The vulnerability was tested manually and the report was carefully read.

req_clen = data->state.infilesize;
result = Curl_creader_set_fread(data, req_clen);
...
curlx_dyn_addf(reqp, "Content-Length: %" FMT_OFF_T "\r\n", req_clen);