avformat/dv: implement fallback in dv_extract_pack()

Fixes Ticket2340
Fixes Ticket2341

Based-on mail from Dave Rice <dave@dericed.com>
Tested-by: Dave Rice <dave@dericed.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 88f038ac97a875f25c2eceac6d2107a09314984c)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
libavformat/img2dec.c: Add a long_name to the piped image demuxers

This fixes segfaults in gst-libav1.0 compiled against FFmpeg 2.3.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 135ea609cebb5a5d331a2550caebe161d163c190)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
doc/APIchanges: mention FF_INPUT_BUFFER_PADDING_SIZE chage

Suggested-by: Andreas Cadhalpun
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 94c4ad27dc6305a7e1f218b86311db019e41f632)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
RELEASE_NOTES: fix WebVTT decoder typo (-> encoder)

Found-by: Clément Bœsch <u@pkh.me>
Signed-off-by: Timothy Gu <timothygu99@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 065fa668723687eba234ba93bc9aa532d68c8d1c)

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