netfilter: xt_conntrack: Add flag to support aliases

The patch adds the flag to denote the "state" alias as of the subset
of the "conntrack" match.

Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/xt_conntrack.h

@@ -31,6 +31,7 @@ enum {
 	XT_CONNTRACK_REPLSRC_PORT = 1 << 10,
 	XT_CONNTRACK_REPLDST_PORT = 1 << 11,
 	XT_CONNTRACK_DIRECTION    = 1 << 12,
+	XT_CONNTRACK_STATE_ALIAS  = 1 << 13,
 };
 
 struct xt_conntrack_mtinfo1 {