Currently we draw the polyline from the input polygon, but we
should first create a trapezoid and draw its polygons when drawing
the hairline.

Change-Id: Idd850d18d05410c75a8a2c922338caf46158bfd4
(cherry picked from commit c9d39c37)
Reviewed-on: https://gerrit.libreoffice.org/18105Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>