Fix the really obvious errors found in various places trying to track down
the arts bug.
 - wrong function prototypes in ao_null and ao_wav
 - freeing stuff based on wrong tests in audio_out.c
 - fix a memory leak in ao_arts.c


git-svn-id: http://svn.xiph.org/trunk/ao@1375 0101bb08-14d6-0310-b084-bc0e0c8e3800