bug#25292: Ambiguity in doc string of defvar

[Eli Zaretskii]

> Date: Thu, 29 Dec 2016 19:42:38 +0000
> Cc: 25292@debbugs.gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
>     If SYMBOL's value is void and the optional argument INITVALUE is
>     provided, INITVALUE is evaluated and the result used to set SYMBOL.
                                                           ^^^^^^^^^^^^^
"...to set SYMBOL's value."

>     If SYMBOL is buffer-local, its default value is what is set;
>     buffer-local values are not affected.  If INITVALUE is missing,
>     SYMBOL's value is not set.
>  
> What do you think?

Other than that, LGTM, thanks.