- Changed 'while' loops into 'loop'-type loops with a lifetime, thus eliminating 'running' variable
- Moved 'use' statements out of the loop (one time is enought)
* The `keycode` and `scancode` modules only contained a single enum each, so
it makes more sense to put them into the `keyboard` module.
* KeyCode -> Keycode, ScanCode -> Scancode.
A small detail, but this is consistent with SDL_Keycode and SDL_Scancode.