Timeout event implementation:

Timeout event implementation:
The daemon side of this is mostly the same as the patch I sent out.  To select
a timeout period different than the default and to get the timeout period,
I added two library calls, dm_set_event_timeout() and dm_get_event_timeout().
If people are against them, the other option is to tack extra arguments onto
dm_regiser_for_event() and dm_get_registered_device().  I also added a
-t option to dmevent, so people can try out timeouts.