QSvgGenerator does not generate correct vector-effect.

QSvgGenerator sets vector-effect to "non-scaling-stroke" by default on the top-level g-node, but according to the SVG specification, the vector-effect is not inherited and has thus no effect on the child nodes. vector-effect needs to be set explicitly to "inherit" or "non-scaling-stroke" on each element with a cosmetic stroke, or set to "none" or omitted on non-cosmetic strokes. To reproduce, run the svggenerator example and generate a car on a road. The outline of the car should have vector-effect="non-scaling-stroke" and the stripes on the road should have vector-effect="none" or no vector-effect specified at all.