vmm enabled on OpenBSD

As per undeadly.org:

With a small commit, OpenBSD now has a hypervisor and virtualization in-tree. This has been a lot of hard work by Mike Larkin, Reyk Flöter, and many others.

VMM requires certain hardware features (Intel Nehalem or later, and virtualization enabled in the BIOS) in order to provide VM services, and currently only supports OpenBSD guests.