(timeclock-workday-remaining): Changed logic for determining how much

(timeclock-workday-remaining): Changed logic for determining how much
time is remaining.
(timeclock-workday-elapsed): Don't accept a "relative" argument for
the current day's elapsed time.  What could that have meant?
(timeclock-workday-elapsed-string): No "relative" argument anymore.
(timeclock-when-to-leave): Changed logic, similarly to what was done
for `timeclock-workday-remaining'.
(timeclock-find-discrep): Removed "today-only" argument, which had no
meaning.  Fixed some more math problems.  The function now returns a
three member list: (TOTAL-TIME-DISCREPANCY TODAYS-TIME-DISCREPANCY
TODAYS-ELAPSED-TIME).