[AD] xwin color-conversion

["Henrik Stokseth" <hensto@xxxxxxxxxx>]

anyone familiar with the color-conversion on the xwin driver? peter wang or
george foot perhaps?

i have spent two days now examining and experimenting with the xwin driver
to see if the assembler color-conversion can be integrated in SOME cases.
(task listed in todo file) but there are cases where remote and local
endianness is different, (which can be handled by a slow visual method) and
much more commonly bit-shifts which doesn't match allegro's standard,
typically RGB->BGR conversion, something which is currently handled by rmap,
gmap and bmap.

so... questions for daring souls:

1) can we assume that x-windows visuals for the most doesn't use weird
bit-encodings/bit-masks (such as 6:6:4 for 16 bit, instead of the normal
5:6:5) for standard colordepths?

2) what's the best method for handling non-allegro-compatible bit-shifts?
    - keep the existing fast visual methods which handles weird bit-shifts
and bit-masks.
    - add new routines to allegro's color conversion blitters that can
handle weird bit-shifts and perhaps bit-masks.

3) the purpose and function of cmap. i am still just very much guessing
here. but as far as i can tell it is used to convert RGB values to RBG
values found in the colormap, which seems to have a max size of 4k entries.
and that the visual is paletted and over 8 bits is going to give me a
headache soon unless someone explains it to me.

And as always: No promises! I do this for fun.

Sincerely Henrik Stokseth.