Several chunked formats (AIFF, IFF,DSF) store ID3 metadata within an 'ID3 '
chunk tag. If such chunks are stored sequentially, it is possible for the
ID3v2 parser to confuse the chunk tag for the ID3 magic number. e.g.

[1st chunk tag ('ID3 ') | chunk size] [ID3 magic number | metadata ...]
[2nd chunk tag ('ID3 ') | chunk size] [ID3 magic number | metadata ...]

Fixes ticket #3530.
Signed-off-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 5331773c)

Conflicts:
	libavformat/dsfdec.c
	libavformat/id3v2.c