Log Message:
youtube-dl: Update net/youtube-dl to 20170915

pkgsrc changes:
* Add a comment about VERSION_DATE and PKGNAME semantic (to better explain the note
  provided by `pkglint -Wall').

Changes:
2017.09.15
----------
Core
* [downloader/fragment] Restart inconsistent incomplete fragment downloads
  (#13731)
* [YoutubeDL] Download raw subtitles files (#12909, #14191)

Extractors
* [condenast] Fix extraction (#14196, #14207)
+ [orf] Add support for f4m stories
* [tv4] Relax URL regular expression (#14206)
* [animeondemand] Bypass geo restriction
+ [animeondemand] Add support for flash videos (#9944)

2017.09.11
----------
Extractors
* [rutube:playlist] Fix suitable (#14166)

2017.09.10
----------
Core
+ [utils] Introduce bool_or_none
* [YoutubeDL] Ensure dir existence for each requested format (#14116)

Extractors
* [fox] Fix extraction (#14147)
* [rutube] Use bool_or_none
* [rutube] Rework and generalize playlist extractors (#13565)
+ [rutube:playlist] Add support for playlists (#13534, #13565)
+ [radiocanada] Add fallback for title extraction (#14145)
* [vk] Use dedicated YouTube embeds extraction routine
* [vice] Use dedicated YouTube embeds extraction routine
* [cracked] Use dedicated YouTube embeds extraction routine
* [chilloutzone] Use dedicated YouTube embeds extraction routine
* [abcnews] Use dedicated YouTube embeds extraction routine
* [youtube] Separate methods for embeds extraction
* [redtube] Fix formats extraction (#14122)
* [arte] Relax unavailability check (#14112)
+ [manyvids] Add support for preview videos from manyvids.com (#14053, #14059)
* [vidme:user] Relax URL regular expression (#14054)
* [bpb] Fix extraction (#14043, #14086)
* [soundcloud] Fix download URL with private tracks (#14093)
* [aliexpress:live] Add support for live.aliexpress.com (#13698, #13707)
* [viidea] Capture and output lecture error message (#14099)
* [radiocanada] Skip unsupported platforms (#14100)