netfilter: xt_NFQUEUE: queue balancing support

Adds support for specifying a range of queues instead of a single queue
id. Flows will be distributed across the given range.

This is useful for multicore systems: Instead of having a single
application read packets from a queue, start multiple
instances on queues x, x+1, .. x+n. Each instance can process
flows independently.

Packets for the same connection are put into the same queue.

Signed-off-by: Holger Eitzenberger <heitzenberger@astaro.com>
Signed-off-by: Florian Westphal <fwestphal@astaro.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>