Partially fix keyboard

[alice-mkh]

1. private int total_buttons_retro_joypad = 15; <- should be 16. Use array.length instead to avoid that in future

2. Set keyboard for player 2 if there's a gamepad.

[Timecraft]

private int total_buttons_retro_joypad = 15; <- should be 16. Use array.length instead to avoid that in future

I’m such a coding newb >.<