Collection of test cases from libGDX and our own tracker
Tests:
- combine triangle area matches polygon area.
- tris have same winding.
- tris don't have duplicates.
- correct number of internal & boundary edges.
- degenerate polys still give topologically correct output.
also checks all possible start-vert offsets, forwards and backwards.
optional OBJ output, for debugging.
- add BLI_stack_count
- add BLI_stack_pop_n to pop into an array
- add BLI_stack_push_r, which returns a pointer that can be filled in
Also remove sanity check in BLI_stack_pop, assert if the stack is empty.