Fix bad autoconf mojo and disable mmap io on the alsa09 driver by default.

The dmix software mixer and some chipsets don't like mmap io.  Long term
need to make this a runtime decision.


git-svn-id: http://svn.xiph.org/trunk/ao@5403 0101bb08-14d6-0310-b084-bc0e0c8e3800