This header isn't public and holds defines for code in os/ directory,
so no need to keep it in the global header dir - it's probably better
off in os/ directory - just like we already have with many others.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1389>