apparent-solar-time zone possible cleanup

[Zefram]

The apparent-solar-time zones seem to be misusing the "zzz" indicator,
and they have poor boundary behaviour.  The attached patch makes these
changes that seem like a good idea to me:

* abbreviation "LAT", for "Local Apparent Time", during the period where
  the zone provides LAT behaviour

* additional apparent-time offset entry for Dec 31 of previous year,
  so that the ruleset provides LAT correctly for the first half of Jan 1

* range of validity of the LAT data defined strictly as starting and
  ending at Jan 1 00:00 UT

* zone marked as disused outside the range of validity of the LAT data

Also, thoughts on apparent solar time more generally: the existing
solar?? files inconveniently can't be merged because the result would have
more than 256 distinct offsets.  However, if the resolution of the offsets
were dropped from 5 s to 10 s, then there would be only 186 distinct
offsets within the range of the equation of time, so we could have an
apparent-time ruleset covering as many years as we're interested in.
That could allow incorporating those rules into the regular Asia/Riyadh
zone, rather than requiring these hacky separate zones.  The apparent-time
ruleset could also be formulaically generated at build time, rather than
explicitly included in the source tarball.

-zefram
-------------- next part --------------
diff -ur tz2011j/solar87 tz2011j.mod0/solar87
--- tz2011j/solar87	2011-06-15 11:43:14.000000000 +0100
+++ tz2011j.mod0/solar87	2011-10-01 14:14:44.000000000 +0100
@@ -14,6 +14,7 @@
 # stored on disk as unsigned chars.
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
+Rule	sol87	1986	only	-	Dec	31	12:02:50s -0:02:50 -
 Rule	sol87	1987	only	-	Jan	1	12:03:20s -0:03:20 -
 Rule	sol87	1987	only	-	Jan	2	12:03:50s -0:03:50 -
 Rule	sol87	1987	only	-	Jan	3	12:04:15s -0:04:15 -
@@ -381,11 +382,11 @@
 Rule	sol87	1987	only	-	Dec	31	12:02:45s -0:02:45 -
 
 # Riyadh is at about 46 degrees 46 minutes East:  3 hrs, 7 mins, 4 secs
-# Before and after 1987, we'll operate on local mean solar time.
+# LAT = Local Apparent Time
 
 # Zone	NAME		GMTOFF	RULES/SAVE	FORMAT	[UNTIL]
-Zone	Asia/Riyadh87	3:07:04	-		zzz	1987
-			3:07:04	sol87		zzz	1988
-			3:07:04	-		zzz
+Zone	Asia/Riyadh87	0	-		zzz	1987 Jan 1 0:00u
+			3:07:04	sol87		LAT	1988 Jan 1 0:00u
+			0	-		zzz
 # For backward compatibility...
 Link	Asia/Riyadh87	Mideast/Riyadh87
diff -ur tz2011j/solar88 tz2011j.mod0/solar88
--- tz2011j/solar88	2011-06-15 11:43:14.000000000 +0100
+++ tz2011j.mod0/solar88	2011-10-01 14:13:23.000000000 +0100
@@ -13,6 +13,7 @@
 # stored on disk as unsigned chars.
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
+Rule	sol88	1987	only	-	Dec	31	12:02:45s -0:02:45 -
 Rule	sol88	1988	only	-	Jan	1	12:03:15s -0:03:15 -
 Rule	sol88	1988	only	-	Jan	2	12:03:40s -0:03:40 -
 Rule	sol88	1988	only	-	Jan	3	12:04:10s -0:04:10 -
@@ -381,11 +382,11 @@
 Rule	sol88	1988	only	-	Dec	31	12:03:05s -0:03:05 -
 
 # Riyadh is at about 46 degrees 46 minutes East:  3 hrs, 7 mins, 4 secs
-# Before and after 1988, we'll operate on local mean solar time.
+# LAT = Local Apparent Time
 
 # Zone	NAME		GMTOFF	RULES/SAVE	FORMAT	[UNTIL]
-Zone	Asia/Riyadh88	3:07:04	-		zzz	1988
-			3:07:04	sol88		zzz	1989
-			3:07:04	-		zzz
+Zone	Asia/Riyadh88	0	-		zzz	1988 Jan 1 0:00u
+			3:07:04	sol88		LAT	1989 Jan 1 0:00u
+			0	-		zzz
 # For backward compatibility...
 Link	Asia/Riyadh88	Mideast/Riyadh88
diff -ur tz2011j/solar89 tz2011j.mod0/solar89
--- tz2011j/solar89	2011-06-15 11:43:14.000000000 +0100
+++ tz2011j.mod0/solar89	2011-10-01 14:13:31.000000000 +0100
@@ -19,6 +19,7 @@
 # stored on disk as unsigned chars.
 
 # Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
+Rule	sol89	1988	only	-	Dec	31	12:03:05s -0:03:05 -
 Rule	sol89	1989	only	-	Jan	1	12:03:35s -0:03:35 -
 Rule	sol89	1989	only	-	Jan	2	12:04:05s -0:04:05 -
 Rule	sol89	1989	only	-	Jan	3	12:04:30s -0:04:30 -
@@ -386,11 +387,11 @@
 Rule	sol89	1989	only	-	Dec	31	12:03:00s -0:03:00 -
 
 # Riyadh is at about 46 degrees 46 minutes East:  3 hrs, 7 mins, 4 secs
-# Before and after 1989, we'll operate on local mean solar time.
+# LAT = Local Apparent Time
 
 # Zone	NAME		GMTOFF	RULES/SAVE	FORMAT	[UNTIL]
-Zone	Asia/Riyadh89	3:07:04	-		zzz	1989
-			3:07:04	sol89		zzz	1990
-			3:07:04	-		zzz
+Zone	Asia/Riyadh89	0	-		zzz	1989 Jan 1 0:00u
+			3:07:04	sol89		LAT	1990 Jan 1 0:00u
+			0	-		zzz
 # For backward compatibility...
 Link	Asia/Riyadh89	Mideast/Riyadh89