capabilities: Add support for securebits flags

This adds securebits flags for start-stop-daemon and supervise-daemon
by adding --secbits option. As a result, the user can specify
securebits the program should run with. see capabilities(7)

sh/start-stop-daemon.sh

@@ -54,6 +54,7 @@ ssd_start()
 		${output_logger_arg} \
 		${error_logger_arg} \
 		${capabilities+--capabilities} "$capabilities" \
+		${secbits:+--secbits} "$secbits" \
 		${procname:+--name} $procname \
 		${pidfile:+--pidfile} $pidfile \
 		${command_user+--user} $command_user \

sh/supervise-daemon.sh

@@ -37,6 +37,7 @@ supervise_start()
 		${healthcheck_delay:+--healthcheck-delay} $healthcheck_delay \
 		${healthcheck_timer:+--healthcheck-timer} $healthcheck_timer \
 		${capabilities+--capabilities} "$capabilities" \
+		${secbits:+--secbits} "$secbits" \
 		${command_user+--user} $command_user \
 		${umask+--umask} $umask \
 		${supervise_daemon_args:-${start_stop_daemon_args}} \