games: gog-gothic-2: Introduce several fixes.

!85 (closed) was merged right when I was about to make some changes to it 😢. Oh well. Here's a separate patch which (hopefully) should fix most of the major issues that might be encountered during the playthrough of the game. The only problem that I've observed so far is some mild stuttering but I'm not entirely sure whether it's universally reproducible because I have no other devices to test this on other than my low-end personal laptop with an integrated graphics card. If I'm able to track down the root of the issue, I'll fix it some time later in a separate merge request, but for now this should do.