stagefright: Query PCM output format and fix bugs

 * Ask the decoder about it's PCM output format instead
   of hardcoding exceptions.
 * Google's AAC codec fails on main profile, skip it.
 * Don't crash on unsupported Windows Media files.

Change-Id: I2bfe19993e8b0cf7ff78b6d4b63465be093ae1d0
av: Various fixes and cleanups

Change-Id: I82225d8cd3e2b3015e6c0e1dd9ddc5ec8abab525