af-packet: add support for BPF filter.

af-packet: add support for BPF filter.

This patch adds support for BPF in AF_PACKET running
mode. The command line syntax is the same as the one
used of PF_RING.
The method is the same too: The pcap_compile__nopcap()
function is used to build the BPF filter. It is then
injected into the kernel with a setsockopt() call. If
the adding of the BPF fail, suricata exit.