Make AAC in Ogg (ogm) work.

Make AAC in Ogg (ogm) work.

This needs the extradata to be extracted.
The approach used is the one MPlayer uses, though it is
unclear whether the 4 bytes extradata that are skipped
should be skipped always or only for AAC.
The AAC parser must be disabled, too, otherwise playback
still does not work.
Fixes trac issue #547.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>