Add rapidhash

[Nicoshev]

Hello,

I wanted to submit 'rapidhash', an improved version of wyhash, to the list of hashes.

There are two variants:

• rapidhash
• rapidhash_unrolled

They compute the same hash, although the unrolled variant has an optimization which should make it run faster on most modern CPUs.

Both should be passing all tests.

They also pass all tests on SMHasher3 (unlike wyhash) and they have an outstanding collision ration when the default seed is used.

The original source code can be found here: https://github.com/Nicoshev/rapidhash

Thanks,
Nicolas

[rurban]

Lgtm. MacOS is PMP_Multilinear