Split maxscale.h to public and private parts

This header defines some general functions and maxscale main() return
values. Most of it is still public, but there were some functions
which were moved to a core header.

server/core/maxscale/maxscale.h

@@ -0,0 +1,38 @@
+#pragma once
+/*
+ * 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 core/maxscale/maxscale.h - The private maxscale general definitions
+ */
+
+#include <maxscale/maxscale.h>
+
+MXS_BEGIN_DECLS
+
+/**
+ * Initiate shutdown of MaxScale.
+ *
+ * This functions informs all threads that they should stop the
+ * processing and exit.
+ *
+ * @return How many times maxscale_shutdown() has been called.
+ */
+int maxscale_shutdown(void);
+
+/**
+ * Reset the start time from which the uptime is calculated.
+ */
+void maxscale_reset_starttime(void);
+
+MXS_END_DECLS