Restore -flipPixels option removed in upstream server-21.1-branch.

https://gitlab.freedesktop.org/xorg/xserver/-/commit/d1c00c859c6676fbb540420c9055788bc19cb18f
Note ScrnInfoRec structure in hw/xfree86/common/xf86str.h isn't reverted
because it isn't used by -flipPixels option so that we can keep ABI
compatibility among xf86-video-foo drivers.

This -flipPixels is mandatory at least by Xorg server users with
xf86-video-wsfb driver on NetBSD/mac68k and SE/30 mono screen
that has "black=1 and white=0" VRAM.

"go for it" by mrg@ on current-users@:
https://mail-index.netbsd.org/current-users/2022/07/24/msg042731.html

initial import of xorg-server-21.1.3

initial import of xorg-server-1.20.10

initial import of xorg-server-1.20.3

initial import of xorg-server-1.18.4