rust-index: results comparison helper with details
This is a bit simpler to call and has the advantage of systematically log
the encountered deviation.
To avoid committing dead code, we apply it to the `pack_header` method, that
was already returning the Rust result.
Greg Ward, author of the original bfiles extension
Na'Tosha Bard of Unity Technologies
Fog Creek Software
Special thanks to the University of Toronto and the UCOSP program