fate: Add EXIF test.
avcodec/flashsv: check diff_start/height

Fixes out of array accesses
Fixes Ticket2844

Found-by: ami_stuff
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
pngdec: frame multithreading support

Signed-off-by: Paul B Mahol <onemda@gmail.com>