Goal of this commit is to support NGons for boolean modifier
(currently mesh is being tessellated before performing boolean
operation) and also solve the limitation of loosing edge custom
data layers after boolean operation is performed.
Main idea is to make it so boolean modifier uses Carve library
directly via it's C-API, avoiding BSP intermediate level which
was doubling amount of memory needed for the operation and which
also used quite reasonable amount of overhead time.
Perhaps memory usage and CPU usage are the same after all the
features are implemented but we've got support now:
- ORIGINDEX for all the geometry
- Interpolation of edge custom data (seams, crease)
- NGons support
Triangulation rule is changed now as well, so now non-flat
polygons are not being merged back after Carve work. This is
so because it's not so trivial to support for NGons and
having different behavior for quads and NGons is even more
creepy.
Reviewers: lukastoenne, campbellbarton
Differential Revision: https://developer.blender.org/D274
