bug#18059: 24.3.92; defvar and special variables

[Eli Zaretskii]

> From: Michael Heerdegen <michael_heerdegen@web.de>
> Date: Sun, 11 Feb 2018 00:59:10 +0100
> Cc: 18059@debbugs.gnu.org
> 
> Hello Noam,
> 
> thanks for working on this.

Seconded.

> > +Note that specifying a value, even @code{nil}, marks the variable as
> > +special permanently.  Whereas if @var{value} is omitted then the
> > +variable is only marked special locally (i.e. within the current file

A minor Texinfo nit: if you want to use "i.e." without a following
comma, you need to follow it with "@:", to tell TeX this period
doesn't end a sentence.