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

[Drew Adams <drew.adams@oracle.com>]

> No other effect, cursor-in-echo-area was necessary when
> 'read-char-choice' relied on 'read-key'.

Seriously?  You've not only introduced a new function,
`read-char-from-minibuffer', AND used it here and there
(everywhere?) in place of `read-char` and `read-key`,
but you've ALSO changed the behavior of `read-char-choice`,
so it too no longer reads a char in the longstanding,
useful way, which we can count to NOT use the minibuffer?

FTR, here's one user who strongly objects.  You knew that,
generally.  Now you know it for `read-char-choice' in
particular.  Hey, why didn't you just redefine `read-char'
while you were at it?

> Then what remains in 'read-char-choice' after this clean-up,
> is just a call to 'read-char-from-minibuffer' and handling 'help-char'
> by calling 'help-form-show'.  OTOH, 'help-form-show' can be simply
> bound
> to 'help-char' in 'read-char-from-minibuffer-map'.  So I'm lost what
> would be better to do.  I see 2 variants:
> 
> 1. Declare 'read-char-choice' as an equivalent of 'read-char-from-
>    minibuffer', but with additional handling of 'help-char';
> 
> 2. Add handling of 'help-char' to 'read-char-from-minibuffer',
>    and leave 'read-char-choice' unchanged, then replace all calls
>    of 'read-char-choice' with 'read-char-from-minibuffer' calls
>    in the Emacs source tree.

Alas.