bug#1808: 23.0.60; picture-mode not considering double-width characters alignment

[Eli Zaretskii]

> Date: Mon, 11 Jan 2016 20:28:07 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: poppyer@gmail.com, 1808@debbugs.gnu.org
> 
> > From: Alan J Third <alan@idiocy.org>
> > Cc: 1808@debbugs.gnu.org,  poppyer@gmail.com
> > Date: Sun, 10 Jan 2016 20:11:45 +0000
> > 
> > I've written a small patch that I think fixes all these issues.
> > 
> > It works out how many columns the characters that are about to be
> > over-written take up, then deletes them as before, and finally inserts a
> > number of spaces to fill the gap (if they're needed). Then the old code
> > inserts the new character.
> > 
> > Spaces seemed the like the safest option, but it could be easily changed.
> 
> Thanks, this looks correct to me.  Please commit, and I think we can
> close the bug.

Fixed with commit b70dba4 for Emacs 25.1.

Closing.