so that we flush out various code using Bitmap, in favour of using
BitmapEx.
This is part of the process of making Bitmap largely an internal detail
of vcl

Change-Id: Iaf2ead5e3d9960838723fb55b812b97108093d74
Reviewed-on: https://gerrit.libreoffice.org/55062Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>