Tieredsort: Header only, blazing fast (3-4x) C++17 sorting for numeric types

Tieredsort seems like a good balance between performance and complexity. Enough complexity (yet still relatively simple) to get very good performance.

5364 vs 1492 is not 3.6x faster. It's 3.6x as fast or 2.6x faster.

Slop.

https://github.com/Cranot/tieredsort/blob/4091f66c31b4d2f8a1...