Move out-of-scope UTC+2 African zones to 'backzone'.

* africa (Africa/Blantyre, Africa/Bujumbura, Africa/Gaborone)
(Africa/Harare, Africa/Kigali, Africa/Lubumbashi, Africa/Lusaka):
Change these from zones to links to Africa/Maputo.
(Africa/Maseru, Africa/Mbabane):
Change these from zones to links to Africa/Johannesburg.
* backzone: Move the old data here.
* checktab.awk (tztab): Remove special cases for these zones.
* NEWS: Document the above.

africa

@@ -110,23 +110,13 @@ Zone	Africa/Algiers	0:12:12 -	LMT	1891 Mar 15  0:01
 # See Africa/Lagos.
 
 # Botswana
-# From Paul Eggert (2013-02-21):
-# Milne says they were regulated by the Cape Town Signal in 1899;
-# assume they switched to 2:00 when Cape Town did.
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Africa/Gaborone	1:43:40 -	LMT	1885
-			1:30	-	SAST	1903 Mar
-			2:00	-	CAT	1943 Sep 19  2:00
-			2:00	1:00	CAST	1944 Mar 19  2:00
-			2:00	-	CAT
+# See Africa/Maputo.
 
 # Burkina Faso
 # See Africa/Abidjan.
 
 # Burundi
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone Africa/Bujumbura	1:57:28	-	LMT	1890
-			2:00	-	CAT
+# See Africa/Maputo.
 
 # Cameroon
 # See Africa/Lagos.
@@ -161,10 +151,7 @@ Zone	Indian/Comoro	2:53:04 -	LMT	1911 Jul # Moroni, Gran Comoro
 			3:00	-	EAT
 
 # Democratic Republic of the Congo
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone Africa/Lubumbashi	1:49:52 -	LMT	1897 Nov 9
-			2:00	-	CAT
-# The above is for the eastern part; see Africa/Lagos for the western part.
+# See Africa/Lagos for the western part and Africa/Maputo for the eastern.
 
 # Republic of the Congo
 # See Africa/Lagos.
@@ -466,11 +453,7 @@ Zone	Africa/Nairobi	2:27:16	-	LMT	1928 Jul
 			3:00	-	EAT
 
 # Lesotho
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Africa/Maseru	1:50:00 -	LMT	1903 Mar
-			2:00	-	SAST	1943 Sep 19  2:00
-			2:00	1:00	SAST	1944 Mar 19  2:00
-			2:00	-	SAST
+# See Africa/Johannesburg.
 
 # Liberia
 # From Paul Eggert (2006-03-22):
@@ -552,9 +535,7 @@ Zone Indian/Antananarivo 3:10:04 -	LMT	1911 Jul
 			3:00	-	EAT
 
 # Malawi
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Africa/Blantyre	2:20:00 -	LMT	1903 Mar
-			2:00	-	CAT
+# See Africa/Maputo.
 
 # Mali
 # Mauritania
@@ -964,6 +945,13 @@ Zone Africa/El_Aaiun	-0:52:48 -	LMT	1934 Jan # El Aaiún
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Africa/Maputo	2:10:20 -	LMT	1903 Mar
 			2:00	-	CAT
+Link Africa/Maputo Africa/Blantyre	# Malawi
+Link Africa/Maputo Africa/Bujumbura	# Burundi
+Link Africa/Maputo Africa/Gaborone	# Botswana
+Link Africa/Maputo Africa/Harare	# Zimbabwe
+Link Africa/Maputo Africa/Kigali	# Rwanda
+Link Africa/Maputo Africa/Lubumbashi	# E Dem. Rep. of Congo
+Link Africa/Maputo Africa/Lusaka	# Zambia
 
 # Namibia
 # The 1994-04-03 transition is from Shanks & Pottenger.
@@ -1031,9 +1019,7 @@ Zone	Indian/Reunion	3:41:52 -	LMT	1911 Jun # Saint-Denis
 # Tromelin - inhabited until at least 1958
 
 # Rwanda
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Africa/Kigali	2:00:16 -	LMT	1935 Jun
-			2:00	-	CAT
+# See Africa/Maputo.
 
 # St Helena
 # See Africa/Abidjan.
@@ -1077,6 +1063,9 @@ Rule	SA	1943	1944	-	Mar	Sun>=15	2:00	0	-
 Zone Africa/Johannesburg 1:52:00 -	LMT	1892 Feb 8
 			1:30	-	SAST	1903 Mar
 			2:00	SA	SAST
+Link Africa/Johannesburg Africa/Maseru	   # Lesotho
+Link Africa/Johannesburg Africa/Mbabane    # Swaziland
+#
 # Marion and Prince Edward Is
 # scientific station since 1947
 # no information
@@ -1104,9 +1093,7 @@ Zone	Africa/Khartoum	2:10:08 -	LMT	1931
 Link Africa/Khartoum Africa/Juba
 
 # Swaziland
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Africa/Mbabane	2:04:24 -	LMT	1903 Mar
-			2:00	-	SAST
+# See Africa/Johannesburg.
 
 # Tanzania
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
@@ -1227,11 +1214,5 @@ Zone	Africa/Kampala	2:09:40 -	LMT	1928 Jul
 			3:00	-	EAT
 
 # Zambia
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Africa/Lusaka	1:53:08 -	LMT	1903 Mar
-			2:00	-	CAT
-
 # Zimbabwe
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Africa/Harare	2:04:12 -	LMT	1903 Mar
-			2:00	-	CAT
+# See Africa/Maputo.