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

[積丹尼 Dan Jacobson]

There is a buffer "*Char Help*" that emacs makes sure the user is never
able to copy. (What if Stallman found out about this?)

First, if the user tries C-x o, to maneuver from the minibuffer into the
*Char Help* buffer, emacs already knows the user will try this trick,
and thwarts it right away, despite C-x not being explicitly listed in
the prompt,

Second, one might think "Oh, the *Char Help* buffer might be left around
later and then we can copy it." Nope, the emacs police have that one
covered too. It is destroyed right away after use, faster than Jim
Phelps' burning classified audio tape in Mission Impossible.

There is only one place that those "you are not allowed to copy" police
cannot control: when viewed with emacs -nw. (Oops, I leaked it.) Else
one's only option is a screenshot.

So where does one encounter this disappearing "*Char Help*" buffer?
Well when using
  C runs the command dired-do-copy (found in dired-mode-map), which is
  an interactive autoloaded compiled Lisp function in ‘dired-aux.el’.

emacs-version "26.3"

And why would one want to copy the contents of the boring "*Char Help*"
buffer? Well, that's the subject of my next bug report...