[GEM Development] More driver updates

[John Elliott]

  Recent changes in the FreeGEM driver world:

* The 256-colour VESA driver is now integrated into the FreeGEM driver source 
 tree. There have been a few more bugfixes in it, related to line and text
 drawing.

* There's an 800x600x16 VESA driver (inspired by Heinz Rath's similar
 driver).

* There's a 640x200x4 Plantronics driver, in case you've got an ATI Graphics
 Solution or a real Plantronics card.

* There are four other drivers which I've included mainly for fun (or for 
homesick Atarians):
  > 320x200x256 VGA
  > 320x200x4   CGA
  > 320x200x4   CGA, reverse video
  > 320x360x4   3270 PC

  These don't support multiple codepages, because they use a 5x7 font (from
X11) and I haven't updated GEM.CPI or the codepage loader to handle 5x7
fonts.

* If you decide to use one of the 4-colour drivers, there's a Desk Accessory 
 included to switch between the two palettes (red/green/yellow and 
 magenta/cyan/white).

-- 
John Elliott