ocaml-crypto: Fork mirage-crypto as crypto package
Rename mirage-crypto to crypto with new library names:
- mirage-crypto -> crypto
- mirage-crypto-rng -> crypto-rng
- mirage-crypto-pk -> crypto-pk
- mirage-crypto-ec -> crypto-ec
Update maintainer, homepage, and dev-repo to point to
git.recoil.org/gazagnaire.org/ocaml-crypto.
Remove lwt, miou, and mirage-specific code.