ffserver: nits & typos

Signed-off-by: Reynaldo H. Verdejo Pinochet <r.verdejo@sisa.samsung.com>
rtspcodes: add full list of RTSP status codes

Also add reason phrases from http://www.ietf.org/rfc/rfc2326.txt
and macro to translate.

Signed-off-by: Reynaldo H. Verdejo Pinochet <r.verdejo@sisa.samsung.com>
ffserver: don't hardcode RTSP status codes

Signed-off-by: Reynaldo H. Verdejo Pinochet <r.verdejo@sisa.samsung.com>