This patch is from erik85, who says:
This patch makes populate_plane inside polymesh_from_trimesh_with_dissolve run in parallel.
On a test file with a boolean between two subdivided cubes (~6 million verts) this gives a 10% speed increase (49.5s to 45s) on my 6 core CPU.
Also there is an optimization of other_tri_if_manifold to skip the contains-call and get the pointer directly.
This reduces CPU time for find_patches from 5s to 2.2s on the same test file.
81366b7d2c