VBE support

[OKUJI Yoshinori]

  I've added VBE support right now. This is not enough for real use
yet, but I checked it in, because it is necessary to test the code in
various environments. I tested it only for ELSA ERAZOR X2 which
supports VBE 3.0.

  If you are willing to test it, follow this instruction:

1. Run the command "vbeprobe" with no argument. This will show the
version number of your VBE card, and the list of VBE modes supported
by your card.

2. Run the command "testvbe" with a VBE mode number. This will switch
to the mode you specify. The command restores the original text mode,
when you hit any key.

3. Report the result. I'd like to know the result, whether it succeeds
or not. When sending a report, please don't forget to mention your
card.

Okuji