bug#19841: 25.0.50; Doc for `transient-mark-mode' should say that highlighting is with face `region'

[Eli Zaretskii]

> Date: Wed, 11 Feb 2015 13:32:24 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> 
> Please update the doc string, the Emacs manual, node `Disabled Transient
> Mark', and the Elisp manual, node `The Mark'.
> 
> While you're at it, please so likewise for the Elisp manual node `The
> Region'.  (At least Emacs manual node `Mark' mentions it.)
> 
> It is not obvious to users which face they can customize to change the
> `transient-mark-mode' highlighting.
> 
> This thread is one indication of the need for this improvement:
> http://lists.gnu.org/archive/html/help-gnu-emacs/2015-02/msg00236.html

I added references to the 'region' face to the 2 doc strings, but left
the manuals alone.  We generally don't mention faces of features where
those features are described; instead, there's a "Standard Faces" node
in the Emacs manual that documents them all in one place.