* Added a 'STATIONS.TIME_STAMP' field to the database.
* Incremented the database version to 356.
* Added an 'RDStation::isOnline()' method.
* Added a 'STATION_PRESENCE' object type to the notification
system.
* Added code to ripcd(8) to provide system presence information.
* Removed vestigal exit monitor code from rdcatchd(8).
Signed-off-by: Fred Gleason <fredg@paravelsystems.com>