mathematical arc for openSCAD

This module works in the trigonometric circle. As a reminder and without wishing to offend you, the trigonometric circle has its 0 which corresponds to the x-axis and its direction of rotation is counterclockwise.
The start value should ever been lower than end value.
In v2, I added a check up of the start and end values to avoid some issues with the computations. I have improved the processing of the angles and reduced the number of polygons to draw to open the circle.
You can use it as a module in your project or include it in your library.