This commit adds support for a UNIX domain socket for bhyve's remote
framebuffer. It enables the use of the graphical console when the bhyve instance
is running in a jail with no networking, for instance. A VNC client running on
the host can then connect to the UNIX domain socket through the filesystem.
Signed-off-by: Quentin Thébault <quentin.thebault@defenso.fr>
Sponsored by: Defenso
MFC after: 1 week