Code review comment for lp:~widelands-dev/widelands/buildicon_playercolors

I looked around the SDLgfx source code real quick and saw that it provides a shrinking method that gives better quality then just using zoom to shrink. I added a quick hack to shrink the image to ballpark the size, then zoomSurface to get it correct. It still looks worse than menu.png, but much better than before. I think we can ship this and see if somebody complains. Or we enhance the image rescaling later anyways.