This is a fork of libsignal-protocol-c, an implementation of Signal's
ratcheting forward secrecy protocol that works in synchronous and asynchronous
messaging. The fork adds support for OMEMO as defined in XEP-0384 versions
0.3.0 and later.

 * OMEMO version 0.3.0 uses the original libsignal-protocol-c implementation
   with its protocol versions 2 and 3.

 * OMEMO version 0.4.0+ is implemented using a new protocol version 4
   internally. In comparison with protocol version 3, it changes:
   *  HKDF info strings
   *  Protocol buffer encoding
   *  Signature scheme (uses XEd25519 instead of custom "Curve25519 signatures")
   *  Specification-compliant double ratchet
   *  Support for Ed25519 public keys
   *  Various serializations
   *  Removes unused functionality