Follow-up to commit 2f8c6047542feb9830602bff1a24101ddecee6a6 , squash another 'M' in verbose mode.
Derive the increment for acc_minlen from the minlen and maxlen parameters instead of hardcoding it to 2500 ms.

This is somewhat more accurate but does make analyzing log files dependent upon those values.
The default is now 2000 ms * 105 / 90 = 2333 ms.
Weaken precondition for processing leap seconds / DST changes to not insist on correct values for p1, p2, p3, and bit 0, 20, 17, 18.

This allows for some bit errors at the time the leap second or DST change occur,
the event must still be annouced and the date and time must still be correct,
either actual or derived.

For processing the announcement the above parities and bit values must
still be correct.

Remove a now obsolete comment.