Fix hang in slideshow.

This fixes fdo#32861, by processing all remaining events after the
post-yield callback comes around (that's supposed to be the time
when the app can spend time on event processing).
diff --git a/sd/source/ui/slideshow/slideshowimpl.cxx b/sd/source/ui/slideshow/slideshowimpl.cxx
index 0f7212b..867e3bd 100644
--- a/sd/source/ui/slideshow/slideshowimpl.cxx
+++ b/sd/source/ui/slideshow/slideshowimpl.cxx
@@ -1875,6 +1875,9 @@ IMPL_LINK( SlideshowImpl, PostYieldListener, void*, EMPTYARG )
{
    Application::EnableNoYieldMode(false);
    Application::RemovePostYieldListener(LINK(this, SlideshowImpl, PostYieldListener));
    Application::Reschedule(true); // fix for fdo#32861 - process
                                   // *all* outstanding events after
                                   // yield is done.
    if (mbDisposed)
        return 0;
    return updateSlideShow();