Include MariaDB Connector-C headers first

The MariaDB Connector-C headers that are built by MaxScale must be
included before any system headers.

Fixed code that explicitly included the <mysql.h> header to use the
<maxscale/protocol/mysql.h> wrapper instead.

include/maxscale/monitor.h

@@ -18,13 +18,13 @@
 
 #include <maxscale/cdefs.h>
 
-#include <mysql.h>
 #include <openssl/sha.h>
 
 #include <maxscale/config.h>
 #include <maxscale/dcb.h>
 #include <maxscale/server.h>
 #include <maxscale/jansson.h>
+#include <maxscale/protocol/mysql.h>
 
 MXS_BEGIN_DECLS