bug#12230: 24.2; revert-buffer in an Info buffer should refresh Info-index-nodes

[Eli Zaretskii]

> From: Juri Linkov <juri@jurta.org>
> Cc: 12230@debbugs.gnu.org
> Date: Mon, 20 Aug 2012 02:39:29 +0300
> 
> >> Since `Info-revert-find-node' is not the right place to clear
> >> the cache because the same problem can occur after killing
> >> the Info buffer and revisiting the same Info manual manually,
> >> perhaps the right fix would be to check the modtime of the Info file
> >> in `Info-find-file' and clear the cache for modified files.
> >
> > That should do the trick, I think.  Thanks.
> 
> Actually there are more caches that should be cleared.
> The following patch should clear them:

Looks good to me, thanks.