bug#12463: 24.2; pos-visible-in-window-p gets slower over time

[Eli Zaretskii]

> From: Juanma Barranquero <lekktu@gmail.com>
> Date: Sat, 22 Sep 2012 21:53:23 +0200
> Cc: cyd@gnu.org, jwalt@garni.ch, 12463@debbugs.gnu.org
> 
> On Sat, Sep 22, 2012 at 9:46 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
> > I think that would leak memory.
> 
> Because of image_types? Can't the memory be xfree'd?

Yes, you can, if you put some code to do that before setting it to
NULL.