Add SDL_Joystick interface because not all joysticks are SDL_Controller compatible

[vanfanel]

Hi David:

I have added back SDL_Joystick interface code, because not all joysticks are compatible with the SDL_GameController interface. For example, my PS1 original pads are not compatible with SDL_GameController, and several wired USB joysticks I have around are also incompatible.
So here is the fix.

[NagyD]

Just to be sure, did you test that this doesn't break controllers that do support SDL_Controller?

[vanfanel]

Yes. All this patch does is create an SDL_Joystick interface ONLY when the SDL_GameController interface does not support that joystick (when it's not present in SDL_gamecontrollerdb.h).
My PSX adapter is now added into SDL_gamecontrollerdb.h, so I have no personal need for this anymore: my PSX pads are SDL_GameController compatible now, and they work perfectly well with this patch.
Anyway, if someone for some reason unknown to me says that it's causing some missbehaviour when using an SDL_GameController compatible device, I'll be the first to admit I was wrong. But it's simple stuff really :)