* In both the 16 color and the VESA mode, the tileset image is loaded
and split into individual tiles; the tiles are then processed into a
form that is compatible with the video mode in use. For 16 color mode,
a tile is processed each time it is displayed, leading to slow
redrawing. For VESA mode, each tile is processed at startup, leading
to long startup times. Both modes are changed so that the tile is
processed once, when it is first displayed, and the result is cached.
* Use memcpy when splitting the image into tiles.
* Only load the tileset once. In 16 color mode, for reasons I do not
understand, the gr_init function is called twice, leading to delay
in startup. This does not happen in VESA mode.
Ray Chason
af79ad629c