Add Whirlpool and BLAKE2 as opt-in hashes

[ColonelGerdauf]

Whirlpool is part of the ISO standard, whereas BLAKE2 may be useful in cases such as WinRAR.

[sergeevabc]

Firstly, ISO is an umbrella for various recommended things, not all of them are meant for file verification. Whirlpool is slow to compute and long to publish, even adding SHA3 to HashCheck was an overhead.

Secondly, WinRAR uses BLAKE2 internally, i.e. without producing file with checksums to be verified by external apps like HashCheck, let alone there are four types of mentioned algorithm (b, s, bp, sp) but still no agreement which one to use.

The breakthrough in years here is XXHash, which is faster than CRC32 yet far more resistant to collisions.

[sergeevabc]

Err… Any progress on adding BLAKE2 (or even XXHash)?