Mark the "val" variable in json_object_object_foreach as unused so the compiler doesn't complain. Fix warnings in the testReplaceExisting test.

json_object.h

@@ -309,7 +309,7 @@ extern void json_object_object_del(struct json_object* obj, const char *key);
 
 # define json_object_object_foreach(obj,key,val) \
 	char *key; \
-	struct json_object *val; \
+	struct json_object *val __attribute__((__unused__)); \
 	for(struct lh_entry *entry ## key = json_object_get_object(obj)->head, *entry_next ## key = NULL; \
 		({ if(entry ## key) { \
 			key = (char*)entry ## key->k; \

tests/testReplaceExisting.c

@@ -74,5 +74,5 @@ int main(int argc, char **argv)
 
 	json_object_put( my_object );
 
-	return 0;
+	return retval;
 }