displaycolordepth parameter doesn't seem do anything

[Miss-Inputs]

On Linux, the displaycolordepth parameter exists, but specifying it in .basilisk_ii_prefs or in the command line appears to have no effect. For example, specifying displaycolordepth 8 should result in the emulated Mac having 256 colours, but it has millions of colours as though it was left unspecified.

This would be useful for some games that require 256 colours or display a warning, etc.

[rickyzhang82]

I added displaycolordepth. It works in SDL1 in Mac and Linux in upstream. It is for 256 color game.

I don't have Windows build stack. The feature has not been tested in SDL2.