Changelog: add missing entries about new mcdeint and sab filters
jpeg2000dec: return error for invalid cdxy values

Fixes division by 0

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
MAINTAINERS: add fingerprint of the FFmpeg release signing key

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>