[sdl2] Lightgun games don't work with the mouse

[tmaul]

Currently the SDL2 port doesn't map the mouse correctly so lightgun games are "less playable". Can be fixed by manually editing the ini files but need to fix so it works by default or the Dinosaurs will win.

[dinkc64]

they must not win!!! :D

[ghost]

what needs added to the config to fix ill start tracking the code if you like unless someone else is doing it.