This makes conn.logs a bit prettier (and smaller) because all lines that
do not use a tunnel will now have a "-" instead of the "(empty)" for
tunnel_parents.
Radiotap support should be fully functional now with Radiotap
packets that include IPv4 and IPv6. Other radiotap packets are
silently ignored. This includes a test which has 802.11 headers
both with and without QoS data.