avcodec/mpeg12dec: drop confusing av_dlog()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/jpeglsdec: ask for sample for "oversized image"

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/jpeglsdec/ff_jpegls_decode_lse: check len field validity

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