The idea is that mpOut is only used for non-drawing purposes outside
Paint(), e.g. to do logic <-> pixel conversion.

Change-Id: Ia83cd32dd0a5152dcfc1644e92af08b4ddf4653c
Reviewed-on: https://gerrit.libreoffice.org/16584Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>
(cherry picked from commit 98d2d985)