- improve the interface of rtti to pass meta_obj_t* as parameter of type function to easy to access private/data

- rename some macro with RTTI
- add RTTI_MAGIC in object header
- add new rtti api

src/str.c

@@ -5,13 +5,20 @@
 
 char* toString(var v, ...)
 {
+    meta_obj_t*    obj    = NULL;
     to_string_fn_t method = NULL;
     va_list        ap;
     char*          s = NULL;
 
-    RTTI_GET_METHOD(method, v, toString, toString);
+    obj = RTTI_DATA_TO_OBJ(v);
+    if (RTTI_OBJ_INVALID(obj)) {
+        errno = EINVAL;
+        return NULL;
+    }
+
+    RTTI_GET_METHOD(method, obj, toString, toString);
     if (method == NULL) {
-        errno = -EINVAL;
+        errno = EINVAL;
         return NULL;
     }