ocserv always logged to the syslog daemon(3) facility, making it
impossible to route its messages separately from other daemons.
Adds a syslog-facility config key (and --syslog-facility CLI flag)
accepting daemon/user/auth/authpriv/local0-local7; defaults to daemon.
Resolves: #691
Signed-off-by: Nikos Mavrogiannopoulos <n.mavrogiannopoulos@gmail.com>
