bug#30697: make eval-expression only take `read'-able Lisp

[Charles A. Roelli]

> Date: Sun, 04 Mar 2018 19:10:55 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> CC: 30697@debbugs.gnu.org
> 
> You are changing the behavior of read--expression, which has a few
> callers in Emacs.  Did you verify that those callers won't break due
> to this change?

I've now tested them, and they work fine.  `eval-minibuffer' (which is
used for (interactive "X")) turns out to be one of the callers of
`read--expression', so I think the documentation of that interactive
spec will have to be updated too.

I also did small tests with ido-mode/icomplete-mode enabled, which
also do not seem to be affected by this change.
 
> This should also have a NEWS entry, and perhaps the manual needs some
> changes, please take a look.

Thanks, I will work on that.