expose crypto_shorthash and crypto_generichash functions.

[benoitc]

Would be cool if salt could expose these functions:

https://github.com/jedisct1/libsodium#new-operations

I may have some use of it. Instead of using https://github.com/jedisct1/siphash-erlang

[freza]

I agree, but want to carefully review libsodium implementations and interface for these first. I don't like the names much, and I think internal state for SipHash should be explicit rather than maintained internally. Some applications will want repeatable outputs.