Preliminary MacOS X support. This is a port of the patch contributed by

Timothy J. Wood <tjw@omnigroup.com> to the vorbis-dev list nearly a year
ago.  See http://www.xiph.org/archives/vorbis-dev/200009/0139.html for the
original posting.

I ported this blind, and have only verified that I haven't broken compile
on existing platforms.  It probably doesn't work right now.


git-svn-id: http://svn.xiph.org/trunk/ao@2089 0101bb08-14d6-0310-b084-bc0e0c8e3800