When emerging live version of libXinerama it detected file collision with the installed xineramaproto-1.1.2 (stable). * Detected file collision(s): * * /usr/include/X11/extensions/Xinerama.h * /usr/include/X11/extensions/panoramiXext.h It doesn't happen with the live version of xineramaproto, so maybe it's only necessary to make it depend on the live xineramaproto.
If you use -9999 ebuilds, you're on your own. Please update xineramaproto to 9999. Thanks