Fix 1bpp Xservers on "whitePixel=0, blackPixel=1" VRAMs.

- Don't override pScreen->blackPixel and pScreen->whitePixel
(set in MD server Init functions per -filpPixels option)
on 1bpp servers in merged fbSetupScreen() (merged one
from cfbSetupScrenn and mfbSetupScreen() in old xsrc/xfree)
- Pull mfbCreateColormap() function from old xsrc/xfree tree
and use it on 1bpp servers

Required by forthcoming X11R7'fied ancient Xsun and XsunMono servers:
https://mail-index.netbsd.org/port-sun3/2020/07/17/msg000157.html

Without these fixes, mouse pointers and twm window titlebar etc. are
rendered inverted.

initial import of existing netbsd xorg-server 1.10 sources in the
xorg-server.old subdir.