libsecp256k1 wrapper for OCaml

This library wrap the secp256k1 EC(DSA) library into an OCaml library. At the moment only a subset of functionalities are available:

• Context: create, clone, destroy, randomize
• Elliptic curve: public key creation
• ECDSA: verify, sign, recover
• Schnorr signatures and xonly public keys

All exchanged data (pubkey, signature, seckey) are represented as hex strings.