Add support for logging security related events

This patch introduces the LOG_CONSOLE syslog facility for logging common
events.  In industrial applications aiming for IEC 62443 compliance the
following events are central for system observability:

- Change of runlevel - i.e., starting up, shutting down, upgrade, etc.
  Facility: console, severity: notice
- Service starting
  Facility: console, severity: notice
- Service restarting
  Facility: console, severity: notice
- Service stopping
  Facility: console, severity: notice
- Service failed to start
  Facility: console, severity: warning

The use of facility console for this makes it easier to filter out when
forwarding syslog messages from an embedded system to a remote log sink.
Otherwise messages of facility daemon would be used, which include a lot
more, and mostly irrelevant, information.

Signed-off-by: Jonas Holmberg <jonas.holmberg@westermo.se>
Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/sm.c

@@ -150,6 +150,7 @@ restart:
 		}
 
 		_d("Setting new runlevel --> %d <-- previous %d", runlevel, prevlevel);
+		logit(LOG_CONSOLE | LOG_NOTICE, "%s, entering runlevel %d", INIT_HEADING, runlevel);
 		runlevel_set(prevlevel, runlevel);
 
 		/* Disable login in single-user mode as well as shutdown/reboot */