Hash Saga Part 6 (Whirlpool support)

Dependent on #121, #123, #124, and #125

Whirlpool, like RIPEMD160, adds a long string (b"a" * 1000000) vector. You can validate it by going to http://www.larc.usp.br/~pbarreto/WhirlpoolPage.html, downloading the documentation package, and looking at the ISO test vectors.