Check bit D0 ("Mode supported by hardware configuration") in the

Check bit D0 ("Mode supported by hardware configuration") in the
mode attributes field and reject video modes for which it isn't
set. I don't know why this was always commented out but X checks
it too so I guess it's safe.

The bit is unset e.g. for video modes which are not supported due
to not enough memory being assigned to an onboard graphics adapter
in the BIOS, or if a mode is supported by a laptop's graphics card
but not by its screen.

Reported-by: Joseph Garcia <bsd_usr@yahoo.com>