avformat/utils: do not override pts in h264 when they are provided from the demuxer

Fixes Ticket2143

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 1e5271a9fd6ddcceb083f2185a4bbd8d44c9a813)
avcodec/bink: fix seeking to frame 0

Fixes Ticket3088

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit cb52d6da0a9c88c584a38a9a7a94825565854b7e)

Conflicts:
	libavcodec/bink.c