bug#15117: 24.3.50; doc of `(forward|backward)-*': state return value

[Eli Zaretskii]

> Date: Tue, 11 Feb 2014 10:14:26 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: lekktu@gmail.com, 15117@debbugs.gnu.org, larsi@gnus.org
> 
> 2. I guess you want a separate bug report for fixing the other
> functions themselves, so they return something useful.

It deserves a separate discussion, but I'm not sure their current
non-values constitute a bug.  There's nothing wrong in returning nil.

In any case, each function should be discussed separately, because the
fact that the name starts with "forward-" says nothing about possible
useful values it could return.