HasMirroredGraphics should be called upon by the object using the
OutputDevice. As I'm focussing on Window, which will be shortly decoupled
from OutputDevice, I have changed HasMirroredGraphics into a virtual
function, and introduced a wrapper function of the same name into Window
that calls upon Window's OutputDevice object.

Due to a bug that never appears to have been fully fixed, mirroring in
printing was broken and a workaround ("hotfix" in the code!) was
implemented but never fully fixed. Therefore, I have overridden
HasMirroredGraphics in Printer and just return false.

Change-Id: I9029e2c50cdb339c1e936bed6b92e8b2aac1dcf9
Reviewed-on: https://gerrit.libreoffice.org/7912Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>