It's an OS 9 API that was exposed via Carbon, but is gone in the 10.6 SDK.
 OS X uses CoreAudio. We only had it in here for debugging purposes anyhow,
 as SDL would never use it unless forced to with an environment variable.

It remains in SDL for OS 9, of course.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%403792