(appt-interval): Variable deleted.

(appt-interval): Variable deleted.
(appt-check): For minutes in between appt-display-interval times,
do check, but don't display anything except an updated mode line.
Count against appt-display-interval based on minutes since
first display of this appointment, not based on time of day.
If appt-display-mode-line, force mode line redisplay
whenever appt-mode-string has changed.
(appt-add, appt-delete): Add autoload cookies.
(appt-check): Catch errors from calling `diary'.
(appt-max-time): Renamed from max-time.
(appt-now-displayed, appt-display-count): New variables.
(appt-timer): Don't create one if we already have one.