Look for virtual methods where we can push their definition "down" i.e.
the base virtual method does not need to exist at all, because all the
call-sites are calling the more specific overrides.

Change-Id: Ib8e82637bfb6bc2a06df45de0e289d27344fb3ab
Reviewed-on: https://gerrit.libreoffice.org/51986Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>