virt: Add vboxguest driver for Virtual Box Guest integration UAPI

This commit adds the headers describing the ioctl API for the
/dev/vboxguest device used by the Virtual Box Guest Additions
in Virtual Box virtual machines.

The driver providing the /dev/vboxguest device will allow Virtual Box
Guest Additions features such as copy-and-paste, seamless mode and
OpenGL pass-through.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>