Multiple fixes, OpenBSD related
Multiple fixes, OpenBSD related

- get_wm: Fixes non-EWMH WM detection on OpenBSD by introducing a
  ps_flags array the same way we do for disks. Tested successfully on
  Debian GNU/Linux (this change impacts all OSes).

- get_wm: Adds fvwm support

- get_model: Adds vmm(4) (OpenBSD's KVM counterpart) support

- get_disk: On OpenBSD you can't use df against a /dev/... unless being
root or in the 'operator' group. A separate disks array creation using
awk has been introduced only for this OS.

dylanaraps/fetch,dylanaraps/neofetch,konimex/neofetch