DIGI_AUTODETECT      - let Allegro pick a digital sound driver
      DIGI_NONE            - no digital sound
      DIGI_OSS             - Open Sound System
      DIGI_ESD             - Enlightened Sound Daemon
      DIGI_ARTS            - aRts (Analog Real-Time Synthesizer)
      DIGI_ALSA            - ALSA sound driver
      DIGI_JACK            - JACK sound driver