SHA3 implementation change

Qt 5.9 changed the definition of QCryptographicHash::Sha3_ family of algorithms from the original Keccak definitions to the standardized NIST ones. This change is sensible, but breaks backwards compatibility.

Therefore I would suggest adding `Keccak_` algorithms that use the original definition, enabling applications to maintain backwards compatibility. I would also suggest adding a note to the documentation explaining this situation.