Uses a different file for the C structs of Libretro.
Makes it easier to manage the structure these structures.

Was creating major memory issues, including in the save of state files.

Adds warning on failing to set callbacks.

Should allow simple testing of the core.

Added more pedantic validations preventing simple dummy data from being loaded.

Support for some basic Python testing.
Handling of loading error with proper error propagation.

Made use of const values to store global data.
Polling is done on every tick, supposedly it's the best approach for libretro.

Handling of GameShark RAM banks differently.
Added parsing integer value errors.

Makes use of the most recent save state support in EmuKit.
Thumbnail image support.

Using static methods instead of global functions.