This fixes a data race by deleting the sound exactly when it finishes
playing.
Previously, a data race could happen in
`CleanupFinishedDuplicateSounds`, where the sound would be destroyed
while Aulib was reading from its buffer.
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.
thebigMuh
Gleb Mazovetskiy
Anders Jenbo