including a fix for a rather glaring bug in BitmapTools.cxx

Change-Id: Id9db990b993cfeea9039c5fbaaa91996adeae22a
Reviewed-on: https://gerrit.libreoffice.org/22713Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>