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.
OK, nice! BTW, I tested table.insert in Luajit and is as slow as the page with the benchmark tests states (6 times slower than direct array assignment).