Thick bindings for libsodium

These bindings are thick and I've committed the testcases I was using to serve as examples. They cover the most of the functionality of libsodium, but some are missing the thick counterparts (e.g. most of the detached versions have no thick counterpart as I stuck with the recommended "combined" variants).

https://github.com/jrmarino/libsodium-ada

From John R. Marino