a better way.  Sort the plugin priorities and do them in descending order.
Also makes use of arts/esd functions to test if they are holding the
device or not.  If present, we check the those plugins first and only
use them if they are currently holding the device.


git-svn-id: http://svn.xiph.org/trunk/ao@5136 0101bb08-14d6-0310-b084-bc0e0c8e3800