Some transition, such as those involving clipping, is not displayed when
switching from last to first slide. That is due to the fact that the
leaving slide (the last one) is over the entering slide (the first one).

The issue has been solved by hiding the last slide and placing a view to
it (svg:use) behind the first slide.

The text decoration unit test has been modified.

Change-Id: Iac1d23a1b9834c301b8ae511ea3f81397e5a4229
Reviewed-on: https://gerrit.libreoffice.org/20705Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Marco Cecchetti <mrcekets@gmail.com>