Set the fullscreen option value too when fs state changes

If the fullscreen state was changed via keyboard commands or the slave
interface the option value was not changed. However that value is used
if the VO is reconfigured. Set the option too to avoid switching
back to the previous state in that case.

command.c

@@ -1027,6 +1027,7 @@ static int mp_property_fullscreen(m_option_t *prop, int action, void *arg,
 #endif
 	if (mpctx->video_out->config_ok)
 	    vo_control(mpctx->video_out, VOCTRL_FULLSCREEN, 0);
+        mpctx->opts.fullscreen = vo_fs;
 	return M_PROPERTY_OK;
     default:
 	return m_property_flag(prop, action, arg, &vo_fs);