h264: Allow discarding the cropping information from SPS

Some 3D systems overload the meaning of the field for other purposes.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
lavu: Add av_strnstr()

This is a length limited version of strstr()

Signed-off-by: Vladimir Pantelic <vladoman@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
avfilter: allow setpts filter to use wallclock time for calculations

Signed-off-by: Vladimir Pantelic <vladoman@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>