Slide-show mode improvements

["Peter Goetz" <peter gtz2 gmail com>]

Hi all,

a few days ago I posted some patches on
http://bugzilla.gnome.org/show_bug.cgi?id=560017
fixing two bugs and also improving transitions in slide-show mode.
It's minor fixes but I found them very useful since these bugs are
very annoying whenever you use Slide-show mode to show your photos to
other people.

I would be very happy if these patches made it into the next release. Thanks!

Peter