[SDL] SDL_ConvertSurface wierdness.

[Mattias Engdegård]

>	/* Copy the palette if any */
>	if ( format->palette ) {
>>		memcpy(convert->format->palette->colors,
>			format->palette->colors,
>			format->palette->ncolors * sizeof(SDL_Color));
>	}

urgh, and I thought I went through that code already. There's another
problem here: is palette->ncolors the number of colours actually used in
the palette, or the maximum palette size?

Several image loaders set palette->ncolors to the number of colours in
the colormap of the image, and this can be useful (testpalette uses it).
This means that SDL_SetPalette() (and SDL_SetColors()) which interpret
palette->ncolors as the maximum palette size are doing wrong.
They should use 2**(BitsPerPixel) instead. Right, Sam?