bug#33372: 26.1; check-coding-systems-region docstring is unclear

[Eli Zaretskii]

> From: Allen Li <darkfeline@felesatra.moe>
> Date: Wed, 14 Nov 2018 07:11:42 +0000
> 
> The docstring for check-coding-systems-region docstring is unclear and
> has a typo.
> 
> Attached is a patch fixing it.  The patch is against master, but I
> imagine it can be applied to 26.

Thanks.  I installed on the emacs-26 branch a more thorough fix of the
doc string, since the original one had additional issues.

One comment for the future: "The value is ..." or even just "Value is
..." is standard terminology in Emacs documentation, you will find
gobs of such phrases all over the places.  You will find much fewer
"The return value is ...".  So this particular part of the doc string
is not something that needs fixing, it's just something to get used
to.