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/authenticator/CDCPlainAuth/cdc_plain_auth.c

@@ -143,7 +143,7 @@ static bool cdc_add_new_user(const MODULECMD_ARG *args)
  *
  * @return The module object
  */
-MODULE_INFO* GetModuleObject()
+MODULE_INFO* MXS_CREATE_MODULE()
 {
     static modulecmd_arg_type_t args[] =
     {