bug#33640: 27.0.50; Wrong column when prompt contains combining characters

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Date: Thu, 06 Dec 2018 01:05:24 +0200
> 
> Eli, do you think this fix should be installed to the emacs-26 branch?

Yes, but please also test it with file names that include double-width
characters.  You can find the list of such characters in
characters.el (search for "East Asian Wide" there).  The success
criterion is that minibuffer navigation works with these characters
not worse than C-n/C-p in "normal" buffers.

Thanks.