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/testroute/testroute.c

@@ -46,7 +46,7 @@ typedef struct
  *
  * @return The module object
  */
-MODULE_INFO* GetModuleObject()
+MODULE_INFO* MXS_CREATE_MODULE()
 {
     static ROUTER_OBJECT MyObject =
     {