doc: put iptables version into manpage

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/ip6tables.8.in b/ip6tables.8.in
index 669a961..3b473bf 100644
--- a/ip6tables.8.in
+++ b/ip6tables.8.in
@@ -1,4 +1,4 @@
-.TH IP6TABLES 8 "Jul 03, 2008" "" ""
+.TH IP6TABLES 8 "" "@PACKAGE_AND_VERSION@" "@PACKAGE_AND_VERSION@"
 .\"
 .\" Man page written by Andras Kis-Szabo <kisza@sch.bme.hu>
 .\" It is based on iptables man page.