Replace Africa zones with links when that doesn't lose useful info.

* africa (Africa/Luanda, Africa/Porto-Novo, Africa/Gaborone)
(Africa/Ouagadougou, Africa/Bujumbura, Africa/Douala, Africa/Bangui)
(Indian/Comoro, Africa/Kinshasa, Africa/Lubumbashi, Africa/Brazzaville)
(Africa/Djibouti, Africa/Malabo, Africa/Asmara, Africa/Addis_Ababa)
(Africa/Libreville, Africa/Banjul, Africa/Accra, Africa/Conakry)
(Africa/Maseru, Indian/Antananarivo, Africa/Blantyre, Africa/Bamako)
(Africa/Nouakchott, Indian/Mayotte, Africa/Maputo, Africa/Niamey)
(Africa/Kigali, Atlantic/St_Helena, Africa/Sao_Tome, Africa/Dakar)
(Africa/Freetown, Africa/Mogadishu, Africa/Mbabane, Africa/Dar_es_Salaam)
(Africa/Lome, Africa/Kampala, Africa/Lusaka, Africa/Harare):
* antarctica (Antarctica/Syowa):
Remove zone, replacing each with a link to a region that has had
the same UTC offset since 1970.
* NEWS: Document this.