[tz] [PROPOSED 2/3] Clarify comment saying “no longer used”

[Paul Eggert]

* africa: Make it clear that the rarer African abbreviations are
still used in the data, even if only in older timestamps.
---
 africa | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/africa b/africa
index 84e1ce2..eb7f8ae 100644
--- a/africa
+++ b/africa
@@ -6,7 +6,7 @@
 # tz at iana.org for general use in the future).  For more, please see
 # the file CONTRIBUTING in the tz distribution.
 
-# From Paul Eggert (2017-04-09):
+# From Paul Eggert (2018-05-27):
 #
 # Unless otherwise specified, the source for data through 1990 is:
 # Thomas G. Shanks and Rique Pottenger, The International Atlas (6th edition),
@@ -51,13 +51,15 @@
 # I vaguely recall 'WAT' also being used for -01 in the past but
 # cannot now come up with solid citations.
 #
-# I invented the following abbreviations; corrections are welcome!
-#	 +02	WAST	West Africa Summer Time (no longer used)
-#	 +03	CAST	Central Africa Summer Time (no longer used)
-#	 +03	SAST	South Africa Summer Time (no longer used)
+# I invented the following abbreviations in the 1990s:
+#	 +02	WAST	West Africa Summer Time
+#	 +03	CAST	Central Africa Summer Time
+#	 +03	SAST	South Africa Summer Time
 #	 +03	EAT	East Africa Time
-# 'EAT' also seems to have caught on; the others are rare but are paired
-# with better-attested non-DST abbreviations.
+# 'EAT' seems to have caught on and is in current timestamps, and though
+# the other abbreviations are rarer and are only in past timestamps,
+# they are paired with better-attested non-DST abbreviations.
+# Corrections are welcome.
 
 # Algeria
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
-- 
2.17.0