OSK-sdl gives feedback on missed presses

Using an encrypted Byzantium and entering the password multiple times a day due to reboots, I'm getting a lot of failed attempts due to imprecise feedback.

Currently, it buzzes on any touch, even if it doesn't cause any other interaction. It would be better to buzz only on accepted presses.

I'm not sure how closely we are tracking upstream, so in case it's already solved there, I'm only filing here.