Add an HE-AAC v1 decoder.

      A large portion of this code was orignally authored by Robert Swain. The rest
was written by me. Full history is available at:
svn://svn.ffmpeg.org/soc/aac-sbr
http://github.com/aconverse/ffmpeg-heaac/tree/sbr_pub

Originally committed as revision 22316 to svn://svn.ffmpeg.org/ffmpeg/trunk