lavf/mov.c: Prevent memory leak in case of invalid metadata reads.

Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
lavfi/afade: fix cur_sample computation

Use the correct timebase conversion.
lavfi/concat: accept a single segment

Simplify scripting operations, so that n=1 is not to be considered as a
special case.
doc/ffmpeg.texi: document the new -start_at_zero option

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/mjpegdec: Support 24111100 pix fmt id

Fixes 129533924_640.jpg

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