Added autodetect_ignore_special_keys option.

I've been playing with my JXD S7800B and found really weird behavior with auto-detecting controllers.

When I press on-board gamepad buttons or move analog It's detected as "ADC joystick" which is correct.
But when I press special keys like volume/back/menu, It's detected as "rk29-keypad".

If i adjust volume/press menu button at first launch(or after switching apps), wrong controller takes Player 1 so I can't control games.

I thought various ways to fixing this problem but I think adding it as option is best solution now.