A quick update to get Sinden Lightguns working on Pi5.

Calibration has been fixed to use SDL2 as SDL1.2 wasn't working.

Calibration is hardcoded to 1920x1080, it should work on a higher resolution but will be a smaller window, probably won't work on a lower resolution.

It is recommended to do this before installing, as I needed to do this for SDL2 to correctly install:
sudo apt-get update
sudo apt-get upgrade

I've only tested calibration with one lightgun, as this is a work in progress.
