minor cleanup
Hoo boy... added hack to make VBE 1.2 modes (0x100-0x11F) selectable
between 24/32bpp by a dosbox.conf configuration parameter. Because some
demos (COMA "parhaat") assume mode 0x10F is 24bpp, and some demos
("Phenomenon") assume mode 0x10F is 32bpp. Eugh. So if Parhaat comes up
with a garbled display, set 'vesa vbe 1.2 modes are 32bpp=false', and
when Phenomenon complains that 320x200 16M colors is not available, set
'vesa vbe 1.2 modes are 32bpp=true' (Hey, at least the Phenomenon demo
actually queries the VESA BIOS to check the mode!).