bug#30405: 26.0.91; Incorrect apostrophe translation in ImageMagick error message

[Eli Zaretskii]

> From: Noam Postavsky <npostavs@users.sourceforge.net>
> Date: Fri, 09 Feb 2018 22:07:06 -0500
> Cc: Gemini Lasswell <gazally@runbox.com>, Paul Eggert <eggert@cs.ucla.edu>,
>       30405@debbugs.gnu.org
> 
> The issue with message producing fancy quotes is new in 25.1, although
> stepping with the debugger, it looks like the root cause is that the
> " *Echo Area 0*" buffer becomes unibyte along with the main buffer.  So
> the following shows the problem in earlier versions as well:
> 
> (set-buffer-multibyte nil)
> (message "can\u2019t")

This is the intended behavior, not a bug.  We make the echo area
buffer unibyte when the message is generated with the current buffer
being unibyte.