Moving selection on Disk Select Menu (F3) very diffult when using PC joystick

[ghedger]

No explanation for this, will look at it if I have time.

Using a PC joystick (a Sony DualShock 4 in my case) for joystick input works. However, moving the selection up and down is extremely difficult. This is no doubt in part due to the grotesque need for a refactor of the Disk Select menu I'm not even sure it's event-driven -- might read SDL keydown directly, don't know, haven't investigated, don't even remember without getting back into the code how SDL 1.2 does this.

At any rate, it makes using the emulator difficult when using a PC Joystick.