* New in version 0.1.8

Netlink devices now support a 'point-to-point' mode.  In this mode the
netlink device does not require an IP address; instead, the IP address
of the other end of the tunnel is specified using the 'ptp-address'
option.  Precisely one site must be configured to use the netlink
device.

The tunnel code in site.c now initiates a key setup if the
reverse-transform function fails (wrong key, bad MAC, too much skew,
etc.) - this should make secnet more reliable on dodgy links, which
are much more common than links with active attackers...  (an attacker
can now force a new key setup by replaying an old packet, but apart
from minor denial of service on slow links or machines this won't
achieve them much).

The sequence number skew detection code in transform.c now only
complains about 'reverse skew' - replays of packets that are too
old. 'Forward skew' (gaps in the sequence numbers of received packets)
is now tolerated silently, to cope with large amounts of packet loss.