Add workaround for loading partial circles from OO

When saving a partion circle/ellipse LO/OO saved the svg:width, svg:height
svg:x and svg:y as there would be a full circle. However according to ODF the
values should be dervived from the bounding box of the displayed shape.

This fixes the problem that the circles in the file attached to the bugreport are displayed
correctly.

OK to backport?