Bug#203462: /etc/X11: backup /etc/X11/XF86Config-4 on dpkg-reconfigure

[Dan Jacobson <jidanni@jidanni.org>]

Package: xfree86-common
Version: 4.2.1-9
Severity: minor
File: /etc/X11

# dpkg-reconfigure xserver-xfree86
Wrote X server configuration to /etc/X11/XF86Config-4.

and didn't make a backup anywhere of such a vital file.