This makes the currently semi-public avpriv_aac_parse_header() function
private to libavcodec and adds a proper public API function to return
the parts of the ADTS header required in libavformat.
The AAC decoder and ADTS-to-ASC BSF both require the header decoder
but not full parsing capabilities.
Originally committed as revision 24217 to svn://svn.ffmpeg.org/ffmpeg/trunk
raw_data_block() per ADTS frame)
Patch by Alex Converse ( alex converse gmail com) based on a patch by Robert
Swain ( robert swain gmail com )
Originally committed as revision 16485 to svn://svn.ffmpeg.org/ffmpeg/trunk