Add '@' to thing-at-point-file-name-chars ?

[Tino Calancha]

Hi Emacs,

following question arose in Bug#24606 and
https://lists.gnu.org/archive/html/emacs-devel/2016-07/msg01219.html

Currently, `thing-at-point-file-name-chars' doesn't contain '@'.
Some files of systemd has '@' in their names.  For instance,
in my machine,
/lib/systemd/system/address@hidden

For those files (thing-at-point 'filename) will not pick up
the full filename:

(let ((file "/lib/systemd/system/address@hidden"))
  (with-temp-buffer
    (insert file)
    (thing-at-point 'filename)))
=> ".service"

Should we add '@' to 'thing-at-point-file-name-chars' ?

Thanks
Tino