[NETFILTER]: nf_conntrack: /proc compatibility with old connection tracking

This patch adds /proc/net/ip_conntrack, /proc/net/ip_conntrack_expect and
/proc/net/stat/ip_conntrack files to keep old programs using them working.

The /proc/net/ip_conntrack and /proc/net/ip_conntrack_expect files show only
IPv4 entries, the /proc/net/stat/ip_conntrack shows global statistics.

Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 9d89068..3db24f4 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -52,6 +52,7 @@
 {
 	return l3proto->print_tuple(s, tuple) || l4proto->print_tuple(s, tuple);
 }
+EXPORT_SYMBOL_GPL(print_tuple);
 
 #ifdef CONFIG_NF_CT_ACCT
 static unsigned int