Fix 1912-01-01 transition for Portugual & colonies

(Thanks to Michael Deckers.)
* NEWS: Mention this.
* africa (Atlantic/Cape_Verde, Africa/Bissau, Africa/Sao_Tome):
* asia (Asia/Macau):
* backzone (Africa/Luanda):
* europe (Europe/Lisbon, Atlantic/Azores, Atlantic/Madeira):
The 1912-01-01 transition was at 00:00 local time after the
transition, not before the transition.
* africa (Atlantic/Cape_Verde): Assume no transition in 1907.

NEWS

@@ -27,6 +27,14 @@ Unreleased, experimental changes
     Enderbury and Kiritimati skipped New Year's Eve 1994, not
     New Year's Day 1995.  (Thanks to Kerry Shetline.)
 
+    Fix the 1912-01-01 transition for Portugual and its colonies.
+    This transition was at 00:00 according to the new UT offset, not
+    according to the old one.  Also assume that Cape Verde switched on
+    the same date as the rest, not in 1907.  This affects
+    Africa/Bissau, Africa/Sao_Tome, Asia/Macau, Atlantic/Azores,
+    Atlantic/Cape_Verde, Atlantic/Madeira, and Europe/Lisbon.
+    (Thanks to Michael Deckers.)
+
     Fix an off-by-1 error for pre-1913 timestamps in Jamaica and in
     Turks & Caicos.
 

africa

@@ -115,13 +115,13 @@ Zone	Africa/Algiers	0:12:12 -	LMT	1891 Mar 15  0:01
 
 # Cape Verde / Cabo Verde
 #
+# From Paul Eggert (2018-02-16):
 # Shanks gives 1907 for the transition to +02.
-# Perhaps the 1911-05-26 Portuguese decree
-# https://dre.pt/pdf1sdip/1911/05/12500/23132313.pdf
-# merely made it official?
+# For now, ignore that and follow the 1911-05-26 Portuguese decree
+# (see Europe/Lisbon).
 #
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone Atlantic/Cape_Verde -1:34:04 -	LMT	1907        # Praia
+Zone Atlantic/Cape_Verde -1:34:04 -	LMT	1912 Jan 01  2:00u # Praia
 			-2:00	-	-02	1942 Sep
 			-2:00	1:00	-01	1945 Oct 15
 			-2:00	-	-02	1975 Nov 25  2:00
@@ -407,13 +407,13 @@ Zone	Africa/Accra	-0:00:52 -	LMT	1918
 
 # Guinea-Bissau
 #
+# From Paul Eggert (2018-02-16):
 # Shanks gives 1911-05-26 for the transition to WAT,
 # evidently confusing the date of the Portuguese decree
-# https://dre.pt/pdf1sdip/1911/05/12500/23132313.pdf
-# with the date that it took effect, namely 1912-01-01.
+# (see Europe/Lisbon) with the date that it took effect.
 #
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Africa/Bissau	-1:02:20 -	LMT	1912 Jan  1
+Zone	Africa/Bissau	-1:02:20 -	LMT	1912 Jan  1  1:00u
 			-1:00	-	-01	1975
 			 0:00	-	GMT
 
@@ -1056,6 +1056,8 @@ Zone	Indian/Reunion	3:41:52 -	LMT	1911 Jun # Saint-Denis
 
 # São Tomé and Príncipe
 
+# See Europe/Lisbon for info about the 1912 transition.
+
 # From Steffen Thorsen (2018-01-08):
 # Multiple sources tell that São Tomé changed from UTC to UTC+1 as
 # they entered the year 2018.
@@ -1064,7 +1066,7 @@ Zone	Indian/Reunion	3:41:52 -	LMT	1911 Jun # Saint-Denis
 # http://www.mnec.gov.st/index.php/publicacoes/documentos/file/90-decreto-lei-n-25-2017
 
 Zone	Africa/Sao_Tome	 0:26:56 -	LMT	1884
-			-0:36:45 -	LMT	1912 # Lisbon Mean Time
+			-0:36:45 -	LMT	1912 Jan  1 00:00u # Lisbon MT
 			 0:00	-	GMT	2018 Jan  1 01:00
 			 1:00	-	WAT
 

asia

@@ -764,8 +764,9 @@ Rule	Macau	1974	1977	-	Oct	Sun>=15	3:30	0	S
 Rule	Macau	1975	1977	-	Apr	Sun>=15	3:30	1:00	D
 Rule	Macau	1978	1980	-	Apr	Sun>=15	0:00	1:00	D
 Rule	Macau	1978	1980	-	Oct	Sun>=15	0:00	0	S
+# See Europe/Lisbon for info about the 1912 transition.
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone	Asia/Macau	7:34:20 -	LMT	1912 Jan  1
+Zone	Asia/Macau	7:34:20 -	LMT	1911 Dec 31 16:00u
 			8:00	Macau	C%sT
 
 

backzone

@@ -170,13 +170,13 @@ Zone	Africa/Lome	0:04:52 -	LMT	1893
 
 # Angola
 #
+# From Paul Eggert (2018-02-16):
 # Shanks gives 1911-05-26 for the transition to WAT,
 # evidently confusing the date of the Portuguese decree
-# https://dre.pt/pdf1sdip/1911/05/12500/23132313.pdf
-# with the date that it took effect, namely 1912-01-01.
+# (see Europe/Lisbon) with the date that it took effect.
 #
 Zone	Africa/Luanda	0:52:56	-	LMT	1892
-			0:52:04	-	LMT	1912 Jan  1 # Luanda Mean Time?
+			0:52:04	-	LMT	1911 Dec 31 23:00u # Luanda MT?
 			1:00	-	WAT
 
 # Democratic Republic of the Congo (east)

europe

@@ -2140,15 +2140,19 @@ Zone	Europe/Warsaw	1:24:00 -	LMT	1880
 			1:00	EU	CE%sT
 
 # Portugal
-#
+
 # From Paul Eggert (2014-08-11), after a heads-up from Stephen Colebourne:
 # According to a Portuguese decree (1911-05-26)
 # https://dre.pt/application/dir/pdf1sdip/1911/05/12500/23132313.pdf
 # Lisbon was at -0:36:44.68, but switched to GMT on 1912-01-01 at 00:00.
-# Round the old offset to -0:36:45.  This agrees with Willett but disagrees
-# with Shanks, who says the transition occurred on 1911-05-24 at 00:00 for
-# Europe/Lisbon, Atlantic/Azores, and Atlantic/Madeira.
+# Round the old offset to -0:36:45.  This agrees with Willett....
 #
+# From Michael Deckers (2018-02-15):
+# article 5 [of the 1911 decree; Deckers's translation] ...:
+# These dispositions shall enter into force at the instant at which,
+# according to the 2nd article, the civil day January 1, 1912 begins,
+# all clocks therefore having to be advanced or set back correspondingly ...
+
 # From Rui Pedro Salgueiro (1992-11-12):
 # Portugal has recently (September, 27) changed timezone
 # (from WET to MET or CET) to harmonize with EEC.
@@ -2231,7 +2235,7 @@ Rule	Port	1983	only	-	Mar	lastSun	 2:00s	1:00	S
 #
 # Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Europe/Lisbon	-0:36:45 -	LMT	1884
-			-0:36:45 -	LMT	1912 Jan  1 # Lisbon Mean Time
+			-0:36:45 -	LMT	1912 Jan  1  0:00u # Lisbon MT
 			 0:00	Port	WE%sT	1966 Apr  3  2:00
 			 1:00	-	CET	1976 Sep 26  1:00
 			 0:00	Port	WE%sT	1983 Sep 25  1:00s
@@ -2240,7 +2244,7 @@ Zone	Europe/Lisbon	-0:36:45 -	LMT	1884
 			 0:00	EU	WE%sT
 # This Zone can be simplified once we assume zic %z.
 Zone Atlantic/Azores	-1:42:40 -	LMT	1884        # Ponta Delgada
-			-1:54:32 -	HMT	1912 Jan  1 # Horta Mean Time
+			-1:54:32 -	HMT	1912 Jan  1  2:00u # Horta MT
 			-2:00	Port	-02/-01	1942 Apr 25 22:00s
 			-2:00	Port	+00	1942 Aug 15 22:00s
 			-2:00	Port	-02/-01	1943 Apr 17 22:00s
@@ -2256,7 +2260,7 @@ Zone Atlantic/Azores	-1:42:40 -	LMT	1884        # Ponta Delgada
 			-1:00	EU	-01/+00
 # This Zone can be simplified once we assume zic %z.
 Zone Atlantic/Madeira	-1:07:36 -	LMT	1884        # Funchal
-			-1:07:36 -	FMT	1912 Jan  1 # Funchal Mean Time
+			-1:07:36 -	FMT	1912 Jan  1  1:00u # Funchal MT
 			-1:00	Port	-01/+00	1942 Apr 25 22:00s
 			-1:00	Port	+01	1942 Aug 15 22:00s
 			-1:00	Port	-01/+00	1943 Apr 17 22:00s