These functions shouldn't be called by drivers or extensions, thus
shouldn't be exported. Also moving it to separate header, so the
already huge ones aren't cluttered with even more things.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1334>
