netfilter: nfnetlink_queue: batch verdict support

Introduces a new nfnetlink type that applies a given
verdict to all queued packets with an id <= the id in the verdict
message.

If a mark is provided it is applied to all matched packets.

This reduces the number of verdicts that have to be sent.
Applications that make use of this feature need to maintain
a timeout to send a batchverdict periodically to avoid starvation.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>