Patch from Stefan Tibus <sjti@gmx.net> to add support for the AIX audio

devices.  The conditional compilation is a little messy, but I still need
to decide a good way to do that in general.


git-svn-id: http://svn.xiph.org/trunk/ao@4214 0101bb08-14d6-0310-b084-bc0e0c8e3800