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/routing/avrorouter/avro.c

@@ -126,7 +126,7 @@ bool avro_handle_convert(const MODULECMD_ARG *args)
  *
  * @return The module object
  */
-MODULE_INFO* GetModuleObject()
+MODULE_INFO* MXS_CREATE_MODULE()
 {
     spinlock_init(&instlock);
     instances = NULL;