bug#3598: 23.0.94; doc string of frame-root-window

[Eli Zaretskii]

> From: "Drew Adams" <drew.adams@oracle.com>
> Date: Thu, 18 Jun 2009 07:05:11 -0700
> Cc: 
> Reply-To: Drew Adams <drew.adams@oracle.com>, 3598@emacsbugs.donarmstrong.com
> 
> If it is an internal function, then please either do not give it a doc string
> or, preferably, give it one that calls that out explicitly, and please add a
> comment explaining why it is internal.

I see no reason not to have doc strings for internal functions.
Emacs hackers need doc strings from time to time.  Adding "internal
use only" to the doc string is the preferred solution.