Add FreeBSD update detection to syscache.
New commands:
syscache hasupdates: [true/false] Updates available
syscache needsreboot: [true/false] Needs to reboot to finish updates
syscache updatelog: Full text output of the check for updates

This will only run the update check once every 24 hours (or whenever syscache gets restarted), while the reboot needed flag will get updated with every sync (instant check).