libxt_NFQUEUE: add new v1 version with queue-balance option

libxt_NFQUEUE: add new v1 version with queue-balance option

New version that adds support for specifying a queue range instead
of a single queue id.
The kernel will distribute flows across the given queue range.

This is useful for multicore systems, simply start multiple instances
of the userspace program on queues x, x+1, .. x+n and use
"--queue-balance x:x+n".
Packets belonging to the same connection are put into the same queue.

With fixes from Jan Engelhardt.

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