Add bpf-libpcap testing suite

* Makefile
* bpf_libpcap_ts.lua
* ts/pcaps/igalia/COPYRIGHT
* ts/pcaps/igalia/empty.pcap
* ts/pcaps/igalia/one-gigabyte.pcap.xz
* ts/pcaps/ws/COPYRIGHT
* ts/pcaps/ws/telnet-cooked.pcap
* ts/pcaps/ws/tftp_wrq.pcap
* ts/pcaps/ws/v4.pcap
* ts/pcaps/ws/v6.pcap
* ts/tests/0001_plan.ts
* ts/tests/0002_plan.ts

$ make test-bpf-libpcap | grep 'tc id'
tc id 1 PASS
tc id 1 AVG ET 0.000242
tc id 2 PASS
tc id 2 AVG ET 0.000265
tc id 3 PASS
[...]