* writing metadata "author" still doesn't work
  (title and comment works)
  See AVHandler.cc:134
  The metadata can be exported with
  ffmpeg -i test_avifile2.avi -f ffmetadata metadata.txt
  Or use VLC to display metadata.

* addframe.cc: Encoder did not produce proper pts, making some up.

* Problem when creating video with only one frame:
  aviread.cc: AVHandler: Error reading packet after timestamp 0

* Try to merge https://savannah.gnu.org/patch/?7988
