[NETFILTER]: ctnetlink: add support for master tuple event notification and dumping

This patch adds support for master tuple event notification and
dumping.  Conntrackd needs this information to recover related
connections appropriately.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>