If a config directory did not exist, the ini file was
not saved at all.
Only implemented for targets that support `std::filesystem` or `std::experimental::filesystem`.
These are all the targets except nxdk and iOS (only supported on iOS 13+).
1. Do not modify the map after loading. Instead, return string views
(guaranteed to be null-terminated) from look up functions and return
the key directly if not found.
2. Use an `unorded_map` instead of `map` where available (C++20).
Saves a bit of RAM (~50 KiB) and improves lookup performance.
SDL_mixer can only stream a single music track
SDL_audiolib has unlimited streams.
With this change, we finally have streaming sounds (respecting
sfx_STREAM).
Audio options can now also be set via diablo.ini, which should help us
better diagnose the static noise issues.
Anders Jenbo
Gleb Mazovetskiy
Vladimir Olteanu
Felipe Wannmacher
Kalebe Alves
Jmgr