feat(event) rework the prototype of lv_event_cb

It encapsulates all event related parameters into a single lv_event_t obejct.

examples/widgets/win/lv_example_win_1.c

@@ -2,9 +2,11 @@
 #if LV_USE_WIN && LV_BUILD_EXAMPLES
 
 
-static void event_handler(lv_obj_t * obj, lv_event_t event)
+static void event_handler(lv_event_t * e)
 {
-    if(event == LV_EVENT_CLICKED) {
+    lv_event_code_t code = lv_event_get_code(e);
+    lv_obj_t * obj = lv_event_get_target(e);
+    if(code == LV_EVENT_CLICKED) {
         LV_LOG_USER("Button %d clicked", lv_obj_get_child_id(obj));
     }
 }