A <textPath href="#id"> pointing at a basic shape imported as point type
with "textPath has no usable path", as only <path> was followed. SVG 2
allows any basic shape, and Inkscape writes one whenever text is put on
a circle. The shape now becomes its equivalent path as SVG 2 defines
it: circles and ellipses start at 3 o'clock and rounded rects after the
top-left corner, all clockwise; lines, polylines and polygons follow
their points. The shape's transform applies as for a <path>. Shapes
that render nothing (zero radius or size) still fall back to point
type with the warning.
Fixes#1527