#i123817# replaced boost::shared_dynamic_cast in slideshow

Boost's shared_dynamic_cast and shared_static_cast were deprecated since
boost 1.35 and removed in boost 1.53, so they have to be replaced

Found-by: Ariel Constenla-Haile <arielch@apache.org>
Suggested-by: Ariel Constenla-Haile <arielch@apache.org>
Reviewed-by: Herbert Duerr <hdu@apache.org>


git-svn-id: https://svn.apache.org/repos/asf/openoffice/trunk@1564275 13f79535-47bb-0310-9956-ffa450edef68