message: Fix compatibility with OpenSSL 1.1
  OpenSSL 1.1 removed the deprecated HMAC_CTX_init() and
  HMAC_CTX_cleanup() and declared the HMAC_CTX struct private.
  However, as far as I can see HMAC_CTX isn't used at all here,
  so the problematic code can simply be removed
diff: @@ -31,10 +31,6 @@ int compute_HMACSHA256(const char* key, int keylen, const char* msg, int msglen,
  int retval = -1; /* success=0, fail=-1 */
  - /* initialise HMAC context */
  - HMAC_CTX ctx;
  - HMAC_CTX_init(&ctx);
  -
  unsigned char md[EVP_MAX_MD_SIZE + 1]; // EVP_MAX_MD_SIZE=64
  memset(md, 0, sizeof(md));
  unsigned int mdlen;
  @@ -154,9 +150,6 @@ int compute_HMACSHA256(const char* key, int keylen, const char* msg, int msglen,
  }
  }
  - /* cleanup HMAC */
  - HMAC_CTX_cleanup(&ctx);
  -
  return retval;
  }
  