options: handle runtime wid change

Add UPDATE_VO flag to the --wid option so that the window embedding
can be changed at runtime without needing to reset another UPDATE_VO
option.

options/options.c

@@ -168,7 +168,7 @@ static const m_option_t mp_vo_opt_list[] = {
     {"video-unscaled", OPT_CHOICE(unscaled,
         {"no", 0}, {"yes", 1}, {"downscale-big", 2})},
     {"video-recenter", OPT_BOOL(recenter)},
-    {"wid", OPT_INT64(WinID)},
+    {"wid", OPT_INT64(WinID), .flags = UPDATE_VO},
     {"screen", OPT_CHOICE(screen_id, {"default", -1}), M_RANGE(0, 32)},
     {"screen-name", OPT_STRING(screen_name)},
     {"fs-screen", OPT_CHOICE(fsscreen_id, {"all", -2}, {"current", -1}),