netfilter: netns nat: per-netns NAT table

Same story as with iptable_filter, iptables_raw tables.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index a6ed838..b286b84 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -38,6 +38,7 @@
 	struct xt_table		*iptable_raw;
 	struct xt_table		*arptable_filter;
 	struct xt_table		*iptable_security;
+	struct xt_table		*nat_table;
 #endif
 
 	int sysctl_icmp_echo_ignore_all;