part of the process of moving Bitmap usage to BitmapEx

Change-Id: I4f02f8aa60d19a3639d623a998491447adf79e15
Reviewed-on: https://gerrit.libreoffice.org/55031Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>