Right now, it appears to me that icaltime_compare_date_only() can't
possibly do the right thing in all circumstances, because it always
normalizes to UTC and then compares. If I have two icaltime's that are
in the same day in some timezone, but that difference spans midnight
when normalized to UTC, the wrong thing is returned.
I propose to fix this by giving icaltime_compare_date_only() a third
argument: timezone to do the compare in. Both dates would be normalized
to that timezone before comparing. What do folks think -- does this
sound like a reasonable API change?