Xcode: drop X11-related source files from build configurations
Xcode: drop X11-related source files from build configurations

We don't use X11 on Mac, and these cause compilation errors anyway.

Signed-off-by: Steven Noonan <4068f0880b399410602d694b3cc711c8a8f4727e@uplinklabs.net>

crawl/crawl-sdl,crawl/crawl-sdl,crawl/crawl-sdl,crawl/crawl-sdl,crawl/crawl-sdl,crawl/crawl-sdl