Further FreeBSD updates.

Remove the dependency on libkvm and the need for a setgid binary by using
sysctl to determine memory and swap usage.

Based on similar patches for wmmemload.  See:
http://repo.or.cz/w/dockapps.git/commitdiff/a473280ab9850b93ba2da950cb549c62a2225351?hp=ba72863015547316aaed5e9c42fd179faeeaa911
http://sources.debian.net/src/wmmemload/0.1.7-2/debian/patches/sysctl_swap.patch/