I've never given out my real name online, so I'll sort my username as a
last name. My personal preference would have been to sort the list by
first name instead of last name, since that'd be clearer, plus you
often recognize people by their first name rather than their last name.
Follow-up to #19 which did the change for macOS.
It appears to work as expected on Linux too.
Tested on a distro where XDG_DATA_HOME is undefined by default,
and `PHYSFS_getPrefDir` also resolves to `~/.local/share/VVVVVV/`.
The first organization parameter is unused on Linux and macOS.