st/xvmc: Add X11 include path.
This patch fixes this build error. CC tests/xvmc_bench.o In file included from tests/xvmc_bench.c:35: tests/testlib.h:38:10: fatal error: 'X11/Xlib.h' file not found ^~~~~~~~~~~~ Signed-off-by:Vinson Lee <vlee@freedesktop.org> Cc: mesa-stable@lists.freedesktop.org Reviewed-by:
Emil Velikov <emil.velikov@collabora.com> (cherry picked from commit 4f74580d)