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/schemarouter/schemarouter.c

@@ -591,7 +591,7 @@ bool check_shard_status(ROUTER_INSTANCE* router, char* shard)
  *
  * @return The module object
  */
-MODULE_INFO* GetModuleObject()
+MODULE_INFO* MXS_CREATE_MODULE()
 {
     MXS_NOTICE("Initializing Schema Sharding Router.");
     spinlock_init(&instlock);