Blender Git Loki

Fix T38135: Global start and end point of the curve was set to zero radius & weight, when using 'linked' option.

This was (more or less) OK with hand-drawn strokes, as the number of points made it nearly unoticable, but broke completely with line and poly strokes!

Did this when I implemented linked curve feature because it was easier! Now, convert code always adds a heading and trailing point to the curve,
to get initial/final zero radius. Adds even more complexity to those functions... :/