bug#48657: Defvar delimiter for dired-copy-filename-as-kill

[Eli Zaretskii <eliz@gnu.org>]

> From: Rodrigo Morales <moralesrodrigo1100@gmail.com>
> Date: Tue, 25 May 2021 14:12:02 -0500
> 
> (defun dired-copy-filename-as-kill (&optional arg)
> ...
>              (mapconcat #'identity
>                         (if arg
>                             (cond ((zerop (prefix-numeric-value arg))
>                                    (dired-get-marked-files))
>                                   ((consp arg)
>                                    (dired-get-marked-files t))
>                                   (t
>                                    (dired-get-marked-files
> 				    'no-dir (prefix-numeric-value arg))))
>                           (dired-get-marked-files 'no-dir))
>                         " ") ;; <---- [[[ Here's the hardcoded delimiter ]]]
> ...)
> #+END_SRC
> 
> I thought that it would be useful to have a defvar that allows
> specifying the delimiter for copied filenames through the mentioned
> function. Perhaps, its name could be "dired-copy-filename-delimiter".

The only sane value for a reliable delimiter is the null byte, so
maybe it doesn't make much sense to customize it.