Revert some zone-to-link changes and add some more; plus related fixes.

Revert zone-to-link changes that changed current time zone
abbreviations.  Add a few more changes, for more consistency.
Make several other fixes discovered while researching this.
* africa (Africa/Accra, Antarctica/Syowa):
* asia (Pacific/Palau):
* australasia (Pacific/Funafuti, Pacific/Majuro, Pacific/Wake)
(Pacific/Wallis, Antarctica/DumontDUrville, Pacific/Chuuk)
(Pacific/Pohnpei):
* northamerica (Pacific/Tahiti):
Remove links, as they are now zones again.
* africa (Africa/Accra, Africa/Maputo):
* antarctica (Antarctica/DumontDUrville, Antarctica/Syowa):
* australasia (Pacific/Tahiti, Pacific/Majuro, Pacific/Chuuk)
(Pacific/Pohnpei, Pacific/Palau, Pacific/Funafuti, Pacific/Wake)
(Pacific/Wallis):
Restore zone.
* africa (Africa/Accra): Assume DST starting in 1920, as per Scott
Keltie & Epstein 1920.
* asia (Asia/Bahrain, Asia/Phnom_Penh, Asia/Kuwait, Asia/Vientiane)
(Asia/Muscat, Asia/Ho_Chi_Minh, Asia/Aden):
* northamerica (America/Antigua, America/Cayman):
Change from zone to link, as these are also closely related.
* africa (Africa/Blantyre, Africa/Bujumbura, Africa/Gaborone)
(Africa/Harare, Africa/Kigali, Africa/Lubumbashi, Africa/Lusaka):
Now links to Africa/Maputo, not Africa/Johannesburg.
* asia (Asia/Riyadh): Change standard-time transition from 1950
to 1947-03-14.  Add commentary citing Hunt 1961 and CAB 1946.
* australasia (Pacific/Chatham): Assume NZST - 45 min. before 1946.
Add commentary about this.
(Pacific/Pago_Pago): UT-11 from 1911 to 1950.
(WS, Pacific/Apia): Use NZ-style abbreviations.
Switch to "WSST" for Western Samoa standard time before 1950.
Add commentary about Samoa before 1950.
* backward (Africa/Asmera, Africa/Timbuktu, Asia/Saigon):
Redo to avoid link-to-link.
* europe (Hungary, Europe/Bucharest): Several pre-1946
corrections: in 1918 the transition out of DST was on 09-16, not
09-29; in 1919 it was on 11-24, not 09-15; in 1945 it was on
11-01, not 11-03; in 1941 the transition to DST was 04-08 not
04-06 at 02:00; and there was no DST in 1920.
(Poland): Add source for 1919.
* southamerica: Add link for America/Antigua.
* NEWS: Document the above.  Add some thanks.