Merge commit '3ec6f855'

* commit '3ec6f855':
  srt: Adjust signedness of sscanf format strings

This commit is a noop, a different fix is included in the big -Wformat
patch under review
(http://ffmpeg.org/pipermail/ffmpeg-devel/2017-March/209239.html)
Merged-by: Clément Bœsch <u@pkh.me>