Use a way similar to libgtop to get memory usage on FreeBSD
requested to merge wip/lantw/use-a-way-similar-to-libgtop-to-get-memory-usage-on-freebsd into master
Fixes: #176 (closed)
You can find libgtop code here: https://gitlab.gnome.org/GNOME/libgtop/blob/2.40.0/sysdeps/freebsd/mem.c