Add MariaDB Connector/C as a built-in alternative (v3.2.3).

vendor/MDBC/plugins/auth/ref10/common.h

@@ -0,0 +1,23 @@
+/*
+   Copyright (c) 2017, MariaDB
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
+
+#include <mysql.h>
+#include <string.h>
+
+#include "ref10/api.h"
+#include "crypto_sign.h"
+
+#define NONCE_BYTES 32