netfilter: xt_recent: IPv6 support

This updates xt_recent to support the IPv6 address family.
The new /proc/net/xt_recent directory must be used for this.
The old proc interface can also be configured out.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>

Documentation/feature-removal-schedule.txt

@@ -250,6 +250,9 @@ What (Why):
 	- xt_mark match revision 0
 	  (superseded by xt_mark match revision 1)
 
+	- xt_recent: the old ipt_recent proc dir
+	  (superseded by /proc/net/xt_recent)
+
 When:	January 2009 or Linux 2.7.0, whichever comes first
 Why:	Superseded by newer revisions or modules
 Who:	Jan Engelhardt <jengelh@computergmbh.de>

net/netfilter/Kconfig

@@ -743,6 +743,13 @@ config NETFILTER_XT_MATCH_RECENT
 	Short options are available by using 'iptables -m recent -h'
 	Official Website: <http://snowman.net/projects/ipt_recent/>
 
+config NETFILTER_XT_MATCH_RECENT_PROC_COMPAT
+	bool 'Enable obsolete /proc/net/ipt_recent'
+	depends on NETFILTER_XT_MATCH_RECENT && PROC_FS
+	---help---
+	This option enables the old /proc/net/ipt_recent interface,
+	which has been obsoleted by /proc/net/xt_recent.
+
 config NETFILTER_XT_MATCH_SCTP
 	tristate  '"sctp" protocol match support (EXPERIMENTAL)'
 	depends on NETFILTER_XTABLES && EXPERIMENTAL