Update time zone abbreviations lists.

This updates known_abbrevs.txt to be what it should have been already,
were my -P patch not broken; and updates some tznames/ entries that
missed getting any love in previous timezone data updates because zic
failed to flag the change of abbreviation.

The non-cosmetic updates:

* Remove references to "ADT" as "Arabia Daylight Time", an abbreviation
that's been out of use since 2007; therefore, claiming there is a conflict
with "Atlantic Daylight Time" doesn't seem especially helpful.  (We have
left obsolete entries in the files when they didn't conflict with anything,
but that seems like a different situation.)

* Fix entirely incorrect GMT offsets for CKT (Cook Islands), FJT, FJST
(Fiji); we didn't even have them on the proper side of the date line.
(Seems to have been aboriginal errors in our tznames data; there's no
evidence anything actually changed recently.)

* FKST (Falkland Islands Summer Time) is now used all year round, so
don't mark it as a DST abbreviation.

* Update SAKT (Sakhalin) to mean GMT+11 not GMT+10.

In cosmetic changes, I fixed a bunch of wrong (or at least obsolete)
claims about abbreviations not being present in the zic files, and
tried to be consistent about how obsolete abbreviations are labeled.

Note the underlying timezone/data files are still at release 2014e;
this is just trying to get us in sync with what those files actually
say before we go to the next update.