fix RTSP handling (tested with fbxrtspd/1.2 Freebox RTSP server):
- split of OPTIONS was wrong
- session-id is NOT a number but a random string of at least 8
  chars (see http://tools.ietf.org/html/rfc2326#page-16)
- don't print a warning if a Cseq: header (instead of CSeq:) is received