Rewrote fixup contours, now should handle all cases.
Added few more debug draw modes for the demo.
Changed the vertex welding to cope with slight imprecision in y-direction.
- added rcFixupAdjacentContours which adjust adjacent contour sets so that that they share all vertices (still buggy!)
- changed the demo stucture to handle tiled navmesh generation process (still ugly)
- the performance results are put into a struct instead of logged immediatelly
- added ChunkyTriMesh class which allows to partiotion a trimesh to smaller pieces using AABB tree
