Make the IFF demuxer a little more standards-compliant, e.g. respect the size
fields of common media header chunks (these can have different sizes depending
on the type of IFF file you read), better handle odd sizes (like RIFF, every
field is padded to word) and handle headerchunks after the BODY chunk.
Patch by Sebastian Vater <cdgs.basty googlemail com>.
Originally committed as revision 22977 to svn://svn.ffmpeg.org/ffmpeg/trunk