SipHash *is* a cryptographic function, with a 128-bit security level.
However, it is not a regular hash function: a secret key is required,
and knowledge of that key allows collisions to be quickly computed offline.
SipHash is therefore more suitable to be used as a MAC.
The same API as other MACs was implemented in addition to functions directly
returning an integer.
The benchmarks have been updated accordingly.
No changes to the SipHash implementation itself.
