lavf: use initial_padding instead of deprecated delay
Merge commit 'eabdc2a830f1ab1a3f12243eb7e2fba801cb81f0'

* commit 'eabdc2a830f1ab1a3f12243eb7e2fba801cb81f0':
  lavf: use initial_padding instead of deprecated delay

Conflicts:
	libavformat/matroskaenc.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
ffmpeg: Fix stream copy with initial_padding

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