void on_suspend()

Called whenever this item's owner logs off. Called after the on_move()
event. Objects that decay with time (food, bombs, curses, corpses, etc.)
that might be in a player's inventory should use this event to switch
themselves off. The object will then sit in a holding bubble (look for
the 'bank' area in the world object to see all the bubbles) until its
owner logs back on, at which time on_restore will be called.

