Fix incorrect index used for handling POVs 2 to 4 for DirectInput devices

[jaybz]

Because JoystickOffset.PointOfViewControllers1 - 3 are offset by multiples of 4 from JoystickOffset.PointOfViewControllers0, instead of getting indexes of 0, 1, 2, and 3, indexes used were 0, 4, 8, and 12 respectively. This prevented handling of any input events from POVs 2-4. This fix allows POVs 2-4 to work.

EDIT: Added a commit that fixes an issue which prevents DirectInput capabilities reporting for DI devices that have no axes. PR title has been edited. In hindsight, I should have committed this one on a separate branch and created a separate PR for it, but I can't be bothered to muck about with the commits at this point. I can do that later if it is important enough to do so, but please don't make me.