bug#8337: patches that fixes the problem in appt

[Glenn Morris]

Sorry about the delay. I do think this is something that needs to be
fixed, though I don't think it (ie, overlapping appointments) is very
important and I expect to be busy over the next several weeks. Thanks
for sending the patch and rest assured I won't forget about it.

The patch seems far too large to me though, and is hard to follow since
presented as a set of 14 consecutive patches, many of which seem
unrelated to the actual issue. They include a lot of stuff that isn't
directly relevant and that I don't want (deletion/addition of options,
renaming of local variables, what seems like unnecessary refactoring,
etc.). It looks like I've done some of this independently in the
meantime (patches 1, 2, at first glance). Of the rest: 3 and 6 are
entirely cosmetic; 5 is unrelated and incorrect; 10 I don't want, and it
and others like it just make subsequent patches harder to follow.

At first sight, I'd just like the minimum change: appt-check to not stop
at the first relevant entry from appt-time-msg-list, but instead
accumulate all the relevant ones. In case of multiple appointments, the
modeline should just say "Appts in 3,5,...mins", and the appointment
display should just concatenate multiple appts on new lines. No need for
new display options. I don't see that this should require such large
changes. Maybe this is buried down in patch 12 somewhere, but it looks
like it will take some extracting, hence the delay.