Rename fields of Link lines for clarity.

* zic.8, zoneinfo2tdf.pl: Change names of Link line fields to be more
descriptive and more like the parameters of 'ln'.  LINK-FROM becomes
TARGET, and LINK-TO becomes LINK-NAME.
* backward: Add a '# Link' header.
* europe, northamerica: Add a few '# Zone' headers where needed.
* NEWS: Document this.

NEWS

@@ -55,6 +55,10 @@ Unreleased, experimental changes
     A new file CONTRIBUTING is distributed.  (Thanks to Tim Parenti for
     suggesting a CONTRIBUTING file, and to Walter Harms for debugging it.)
 
+    The fields in Link lines have been renamed to be more descriptive
+    and more like the parameters of 'ln'.  LINK-FROM has become TARGET,
+    and LINK-TO has become LINK-NAME.
+
     tz-link.htm mentions Windows Runtime etc. (thanks to Matt Johnson)
     and HP-UX's tztab.
 

backward

@@ -4,6 +4,7 @@
 # This file provides links between current names for time zones
 # and their old names.  Many names changed in late 1993.
 
+# Link	TARGET			LINK-NAME
 Link	Africa/Asmara		Africa/Asmera
 Link	Africa/Abidjan		Africa/Timbuktu
 Link	America/Argentina/Catamarca	America/Argentina/ComodRivadavia

europe

@@ -458,6 +458,8 @@ Zone	Europe/London	-0:01:15 -	LMT	1847 Dec  1  0:00s
 Link	Europe/London	Europe/Jersey
 Link	Europe/London	Europe/Guernsey
 Link	Europe/London	Europe/Isle_of_Man
+
+# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone	Europe/Dublin	-0:25:00 -	LMT	1880 Aug  2
 			-0:25:21 -	DMT	1916 May 21  2:00
 			-0:25:21 1:00	IST	1916 Oct  1  2:00s

northamerica

@@ -589,6 +589,7 @@ Zone America/Adak	 12:13:21 -	LMT	1867 Oct 18
 # Note that 1933-05-21 was a Sunday.
 # We're left to guess the time of day when Act 163 was approved; guess noon.
 
+# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone Pacific/Honolulu	-10:31:26 -	LMT	1896 Jan 13 12:00 #Schmitt&Cox
 			-10:30	-	HST	1933 Apr 30  2:00 #Laws 1933
 			-10:30	1:00	HDT	1933 May 21 12:00 #Laws 1933+12
@@ -596,7 +597,6 @@ Zone Pacific/Honolulu	-10:31:26 -	LMT	1896 Jan 13 12:00 #Schmitt&Cox
 			-10:30	1:00	HDT	1945 Sep 30  2:00 #Schmitt&Cox+2
 			-10:30	-	HST	1947 Jun  8  2:00 #Schmitt&Cox+2
 			-10:00	-	HST
-
 Link Pacific/Honolulu Pacific/Johnston
 
 # Now we turn to US areas that have diverged from the consensus since 1970.
@@ -622,6 +622,7 @@ Link Pacific/Honolulu Pacific/Johnston
 # Shanks says the 1944 experiment came to an end on 1944-03-17.
 # Go with the Arizona State Library instead.
 
+# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
 Zone America/Phoenix	-7:28:18 -	LMT	1883 Nov 18 11:31:42
 			-7:00	US	M%sT	1944 Jan  1  0:01
 			-7:00	-	MST	1944 Apr  1  0:01

zic.8

@@ -398,7 +398,7 @@ A link line has the form
 .nf
 .ti +.5i
 .ta \w'Link\0\0'u +\w'Europe/Istanbul\0\0'u
-Link	LINK-FROM	LINK-TO
+Link	TARGET	LINK-NAME
 .sp
 For example:
 .sp
@@ -407,12 +407,12 @@ Link	Europe/Istanbul	Asia/Istanbul
 .sp
 .fi
 The
-.B LINK-FROM
+.B TARGET
 field should appear as the
 .B NAME
 field in some zone line.
 The
-.B LINK-TO
+.B LINK-NAME
 field is used as an alternate name for that zone;
 it has the same syntax as a zone line's
 .B NAME
@@ -508,7 +508,6 @@ Link	Europe/Zurich	Switzerland
 .in
 .fi
 In this example, the zone is named Europe/Zurich but it has an alias
-
 as Switzerland.  This example says that Zurich was 34 minutes and 8
 seconds west of UT until 1853-07-16 at 00:00, when the legal offset
 was changed to 7\(de\|26\(fm\|22.50\(sd; although this works out to

zoneinfo2tdf.pl

@@ -40,7 +40,7 @@ while (<>) {
     # Rule  NAME  FROM  TO  TYPE  IN  ON  AT  SAVE  LETTER/S
     @fields == 10 or warn "bad rule line";
   } elsif ($type eq 'link') {
-    # Link  LINK-FROM  LINK-TO
+    # Link  TARGET  LINK-NAME
     @fields == 3 or warn "bad link line";
   } elsif ($type eq 'leap') {
     # Leap  YEAR  MONTH  DAY  HH:MM:SS  CORR  R/S