Update to 2.19
- New upstream release 2.19
- Update with the newest data from IANA and Apache httpd
- mp4 preference is video/mp4 (GH#5)
- yt preference is video/vnd.youtube.yt (GH#6)
- 3gp and 3gpp preference is video/3gpp (GH#7)
- Use author-independent source URL