Move headers from server/include to include/maxscale

- Headers now to be included as <maxscale/xyz.h>
- First step, no cleanup of headers has been made. Only moving
  from one place to another + necessary modifications.

include/maxscale/secrets.h

@@ -0,0 +1,59 @@
+#ifndef _SECRETS_H
+#define _SECRETS_H
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+/**
+ * @file secrets.h
+ *
+ * @verbatim
+ * Revision History
+ *
+ * Date         Who                     Description
+ * 23/06/2013   Massimiliano Pinto      Initial implementation
+ *
+ * @endverbatim
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include <openssl/aes.h>
+
+#define MAXSCALE_KEYLEN 32
+#define MAXSCALE_IV_LEN 16
+
+/**
+ * The key structure held in the secrets file
+ */
+typedef struct maxkeys
+{
+    unsigned char enckey[MAXSCALE_KEYLEN];
+    unsigned char initvector[MAXSCALE_IV_LEN];
+} MAXKEYS;
+
+enum
+{
+    MXS_PASSWORD_MAXLEN = 79
+};
+
+extern int  secrets_writeKeys(const char *directory);
+extern char *decryptPassword(const char *);
+extern char *encryptPassword(const char*, const char *);
+
+#endif