bug#39360: Add :extend attribute to show-paren-mode expression face

[Eli Zaretskii]

> Date: Fri, 31 Jan 2020 19:12:19 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 39360@debbugs.gnu.org
> 
> > Cc: 39360@debbugs.gnu.org
> > From: Clément Pit-Claudel <cpitclaudel@gmail.com>
> > Date: Fri, 31 Jan 2020 11:12:37 -0500
> > 
> > I couldn't find a program on my machine that behave like Emacs now does 
> > (highlighting explicit newlines).
> 
> MS Office does.

Also, most text buffers in Emacs have explicit newlines at the end of
each line, so highlighting them is more like LibreOffice and Firefox
do.