drop compat with ancient XFree86 1/2
We still have lots of code pathes for XFree86, which is gone for
aeons now. That's detected by precense of XORG_VERSION_CURRENT define.
Since the whole show is quite complex now, yet just dropping all code pathes
only active if XORG_VERSION_CURRENT isn't defined. Still leaving the places
where Xorg is treated as Xf86 version 4.3.99.902.0 - these are cleaned up later.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/driver/xf86-video-sis/-/merge_requests/8>