Allow disabling QUIT events (quick fix for certain Windows users) — The Sargosian Abyss Steam update #823804

On a small number of Windows systems the game receives a QUIT event immediately after launching from Steam. The QUIT event should only be triggered by the top right X button, and we've been unable to reproduce the issue. As a quick fix, users experiencing this issue can now create a file named "nox.txt" in the game directory. This will cause the game to ignore all QUIT events, but you will still be able to quit the game from the menu.