IMPORT: xxhash: update to v0.8.0 that introduces stable XXH3 variant

A new XXH3 variant of hash functions shows a noticeable improvement in
performance (especially on small data), and also brings 128-bit support,
better inlining and streaming capabilities.

Performance comparison is available here:

  https://github.com/Cyan4973/xxHash/wiki/Performance-comparison
2 files changed