Delayed mode switch

[SukkoPera]

PAL user are often exposed to this problem: game refuses to boot in 60Hz, and freeze the controller so you have to turn the console On and Off, etc. Just for testing games, it' not that boring, but if you want to really play a game for many times, doing this each time could upset.

This idea comes from the SNES's uIGR board from borti.

The goal would be to set an "Auto mode" that would boot in 50Hz, wait for a while for the game booting, then auto switch to 60Hz (i don't think the other way, booting 50 then 60, would be useful for anyone but...)

Parameters could be set by user in the Arduino sketch : refresh at boot, delay, final refresh. This "Auto mode" could be set with the "Start + B + Up" combo.

(Original idea by MoockyLoock)

[SukkoPera]

The mode_switch_delay branch already has some code for this, but it needs improvement and must rebased on the current master branch.