Ancient Linux audio output. Apparently it survived until now, because
some BSDs (but not all) had use of this. But these should work with
ao_sdl or ao_openal too (that's why these AOs exist after all). ao_oss
itself has the problem that it's virtually unmaintainable from my point
of view due to all the subtle (or non-subtle) difference. Look at the
ifdef mess and the multiple code paths (that shouldn't exist) in the
removed source code.