bug#18716: Patch for this bug

[Eli Zaretskii]

> From: Reuben Thomas <rrt@sc3d.org>
> Date: Tue, 8 Nov 2016 17:51:26 +0000
> 
> It makes dired-mark-unmarked-files act case-insensitively.

You meant case-sensitively, I presume.

> Also, it is better than Stefan's suggestion to use auto-mode-case-fold, as 
> when visiting files, the user will
> quickly see if a file has been e.g. visited in the wrong major mode owing to 
> an uppercase filename being
> treated as a lowercase one; whereas in dired-omit-mode, files can be hidden 
> counter to the user's
> expectation, as happened to me with COPYING.LIB, yet it is not obvious 
> (because the file is hidden!).

I don't understand what happened to the comment about *.JPG files on
case-sensitive filesystems, and how does this patch do TRT on
case-insensitive filesystems.

IOW, it sounds like the right solution cannot be so simple, because
this will most probably cause user complaints of the opposite kind.
No?

Btw, if the problem is only with COPYING.LIB, maybe a better
heuristics would be to remove .lib from completion-ignored-extensions,
as it is no longer so widespread where Emacs users dwell?