Expose the EVP_AEAD Interface

[initsecret]

Right now, the EVP_AEAD Interface is the only way to access modern primitives like AES-GCM-SIV and XChaCha20-Poly1305. Exposing it would make it easier for folks to use these primitives in their rust programs.

For use in a different project, I wrote a quick patch that exposes EVP_AEAD in a way heavily inspired by how symm.rs currently exposes EVP_CIPHER.

If you are interested in this, I can clean up my patch (write more examples, come up with a better name than AeadCrypter,...) and submit a PR.

[jyn514]

If you are interested in this, I can clean up my patch (write more examples, come up with a better name than AeadCrypter,...) and submit a PR.

That would be great, thank you!