Fixed some issues in internal anchors of the Adaptive Cubic infill.
The ugly and dangerous implicit casting operators in Line, MultiPoint,
Polyline and Polygon were made explicit.
The offset curve extractor is already quite usable,
though singular cases are still not covered yet
when the offset curve intersects or nearly intersects
a Voronoi vertex.
Removal of the PRINTF_ZU "%zu" Visual Studio printf compatibility macro.
Fixes of a contours self intersection test for collinear segments.
SVG exporter now exports white background, so that the GNOME Eye viewer is usable.
Refactored Arrange interface: remove the union based BedShapeHint, replace it with proper function overloads
WARN: this commit is only intermediate, it does not compile.
