[Freeciv-Dev] (PR#9535) ftwl: supporting 8bpp mode

["Per I. Mathisen" <per@xxxxxxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=9535 >

The problem here is that themes and other graphics resources may not be in
8bpp, or at least not in the same palette.

I basically see three ways to do this:
  1 - Use a standard palette with a good spread of colours, then match as
best as we can dynamically.
  2 - Compile a palette from the colours used, provided that this number
does not exceed 256. If it does not, this is the optimal solution.
  3 - Demand that 8bpp mode uses an 8bpp theme that supplies its own
palette, and it is the theme writer's responsibility to ensure that this
palette works for the other graphics resources used.

  - Per