Blender Git Loki

Polyfill2d: use kd-tree

Simple search for intersections became slow for larger concave ngons (100+)
Tested to work with ngons up to 75k sides, performance is approx ~6x faster then scanfill.

This is a 2D version of BLI_kdtree with modifications:
- nodes can be removed
- an index -> node map is stored (especially for tessellation)