Savestate handling updated and unified (Patreon)

As the NES core got savestates, I also introduced a new savestate handling system that is now complete.

Thanks to Alexey(Sorgelig) we now have 4 slots available to be saved to SDCard and a proper handling for the user was important.

As a result, you can now create and load savestates with either Gamepad, OSD or Keyboard for all 4 Slots.

Furthermore you can decide to use them with permanent save to SDCard or temporary in DDR-RAM only. This way you can create 4 permanent Savestates and additional 4 online savestates.

The new system is already in place in the Lynx release from yesterday and will be in the next release for the NES core. GBA and Gameboy core will also receive this the next few days.

After finishing that, I will continue to evaluate what I will work on next.