Closing a new polyline with a double-click could result in an polyline closed by an extra
vertex rather than by its closed-flag. This has been fixed.
CADPointInPoly, CADCheckPoly and CADPolyAndPoly are new.
They replace WZ Poly Point, WZ Poly Check and WZ Poly Sect, found in the Math plugin package.
The code has changed somewhat, to improve numerical stability.