twn_util.c: show profiles in milliseconds when appropriate, don't include time taken for profile internals

src/twn_loop.c

@@ -214,7 +214,11 @@ static void main_loop(void) {
         if (ctx.window_size_has_changed)
             update_viewport();
         input_state_update(&ctx.input);
+
+        profile_start("game tick");
         game_object_tick();
+        profile_end("game tick");
+
         input_state_update_postframe(&ctx.input);
 
         /* TODO: make it works when ctx.ticks_per_second != 60 */