* leapseconds.awk, NEWS: Also output expiration date comment.

Problem reported by Martin Burnicki in:
http://www.ietf.org/mail-archive/web/tzdist/current/msg01132.html

NEWS

@@ -33,6 +33,9 @@ Unreleased, experimental changes
 
   Changes affecting commentary
 
+    The leapseconds file commentary now mentions the expiration date.
+    (Problem reported by Martin Burnicki.)
+
     Update Mexican Library of Congress URL.
 
 

leapseconds.awk

@@ -37,6 +37,11 @@ BEGIN {
 }
 
 /^ *$/ { next }
+
+/^#\tUpdated through/ || /^#\tFile expires on:/ {
+    last_lines = last_lines $0 "\n"
+}
+
 /^#/ { next }
 
 {
@@ -64,3 +69,7 @@ BEGIN {
     }
     old_TAI_minus_UTC = TAI_minus_UTC
 }
+
+END {
+    printf "\n%s", last_lines
+}