Finally remove X.h from xcb.h, fix broken image tests.
Finally remove X.h from xcb.h, fix broken image tests.

OpenInkpot-archive/iplinux-libxcb,OpenInkpot-archive/iplinux-libxcb,stapelberg/libxcb,topcat/xcb-win32,topcat/xcb-win32,stapelberg/libxcb,topcat/xcb-win32,OpenInkpot-archive/iplinux-libxcb,stapelberg/libxcb,topcat/xcb-win32,topcat/xcb-win32