leave it untouched to make gtk3 rtl spin buttons possible
where the additional mirrorValue contains the region
of the spinbuttons to render within this rectangle

Change-Id: I2648d98ed36373c95947cc4d78e2e54797f01155
Reviewed-on: https://gerrit.libreoffice.org/17940Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>