Fix for strange characters in GRUB 1.91

[Dennis Clarke]

A picture says a 1000 words :

    http://www.blastwave.org/dclarke/grub/grub_1.91/day_01/img_1280.jpg

I was thinking that perhaps simple line drawing with "-" and "+" could
be used for now and that would also work nicely on serial consoles and
old DEV VT units that some of us still use on headless hardware.  So
perhaps a config option in the grub.cfg for charset would be useful.

Dennis