Blender Git Loki

Fix T89564: Spline IK breaks when it is far away from the world origin

The isect_line_sphere algorithm became very imprecise when the line and
the sphere were reasonably far away from the world origin.

This would lead to no intersections being reported even if there was a
guaranteed intersection (line crossing from inside the sphere to the
outside).

To fix this we now use the secant root finding method to get an
intersection point. This is much more stable and robust it seems.