Implement simple failover mode into mysqlmon

The mysqlmon simple failover mode allows it to direct write traffic to a
secondary node. This enables a very simple failover mode with MaxScale
when it is used in a two node master-slave setup.

server/modules/monitor/mysqlmon.h

@@ -50,6 +50,8 @@
  * @endverbatim
  */
 
+#define MYSQLMON_DEFAULT_FAILCOUNT 5
+
 /**
  * The handle for an instance of a MySQL Monitor module
  */
@@ -72,6 +74,9 @@ typedef struct
     char* script; /*< Script to call when state changes occur on servers */
     bool events[MAX_MONITOR_EVENT]; /*< enabled events */
     HASHTABLE *server_info; /**< Contains server specific information */
+    bool failover; /**< If simple failover is enabled */
+    int failcount; /**< How many monitoring cycles servers must be
+                                   down before failover is initiated */
 } MYSQL_MONITOR;
 
 #endif