Flush accumulated input events on iOS

(cherry picked from commit 0348fa264070fc2d64dec6a926fe242b4c2bb6cd)

platform/iphone/os_iphone.mm

@@ -202,6 +202,8 @@ bool OSIPhone::iterate() {
 		return true;
 	}
 
+	input->flush_buffered_events();
+
 	return Main::iteration();
 };