Create a macro for module declarations

The modules are now declared with a common macro. This allows future
additions to the module loading process while also making the loaded
symbol name a constant.

server/modules/monitor/galeramon/galeramon.c

@@ -59,7 +59,7 @@ bool isGaleraEvent(monitor_event_t event);
  *
  * @return The module object
  */
-MODULE_INFO* GetModuleObject()
+MODULE_INFO* MXS_CREATE_MODULE()
 {
     MXS_NOTICE("Initialise the MySQL Galera Monitor module.");