Use game controller APIs instead of the joystick ones to be able to use
the gamepad button DB file.

The SDL.h include is only valid for macOS because of memset_pattern4, on
Windows it is not required.

The character and weapon sprites have been updated.

Remove mapping for gamepad.

Ensure signed values are respected.

Properly add SDL mocks for macOS.

Use library in new subproject.

Extract tests from source directory.