slackbuild.diff does the following things:

- Allows data filenames to be upper/lower/mixed case
- Stops creating an empty "ck.log" file in the cwd
- Stops segfaulting on exit due to double-free bug
- Gets rid of non-functional -3player, -4player,
  -host, and -join options
- Sets the default frameskip to 1. This is because there is no
  way to DECREASE the frameskip from the in-game Options menu,
  and the original default was 2. Anyone who has an old/slow
  enough machine to need frameskip 2 can still set it (increasing
  the frameskip works fine, you just can't decrease it...)