bug#42708: Let users copy "*Char Help*" buffer

[Drew Adams]

> > Could we please know which occurrence you changed,
> > and what the justification is?
> 
> The changed occurrence is 'dired-query',
> and the justification is to fix the bug report #42708.
> 
> Also I checked other 4 occurrences of `read-char-choice' in
> auth-source.el, emacs-lisp/package.el, net/tramp-cmds.el
> and progmodes/octave.el.  But apparently they use more complex
> logic, so replacing them with `read-char-from-minibuffer'
> is not a straightforward task.

Thanks.
That's probably OK.  I'll have to see, in practice.

FWIW, my (Dired+) version of `dired-query' also allows char
`l', which lists the files to be acted on, showing details
per option `diredp-list-file-attributes':

  diredp-list-file-attributes is a variable defined in `dired+.el'.
  Its value is (5 8)

  Documentation:
  Which file attributes `diredp-list-file' uses, and when.
  A list of file attribute numbers means use only the values of those
  attributes.
  A non-list means use all attribute values.