Use kldstat(8) to check for the availability of the if_tun module in the
kernel instead of checking for existance of /dev/tun. The latter causes
tun(8) to allocate new instance, which is not good by itself, but also
on all FreeBSD versions before the very recent -current it causes number
of tun devices to grow each time the script is invoked (and it's invoked
every time when vpnc makes a new connection).
Bump PORTREVISION.
Approved by: MAINTAINER