pflua-match: Work on arrays of packets, not pointers

This change makes the filter function much tidier, but massively increases performance variance on small data sets (it evens out on larger ones). It retains the property of having no CNEWI calls, as does the sink_cnewi branch, but not master.
Sure, if you think it can be worth, go ahead! I was curious about pairs and ipairs because I thought it could be a potential optimization for Snabbswitch.

But as far as I can see, there is no use of pairs nor ipairs in pflua-match currenytly :/