Log Message:
Update net/youtube-dl to youtube-dl-20170818.

Changes:
2017.08.18
----------
Core
* [YoutubeDL] Sanitize byte string format URLs (#13951)
+ [extractor/common] Add support for float durations in _parse_mpd_formats
  (#13919)

Extractors
* [arte] Detect unavailable videos (#13945)
* [generic] Convert redirect URLs to unicode strings (#13951)
* [udemy] Fix paid course detection (#13943)
* [pluralsight] Use RPC API for course extraction (#13937)
+ [clippit] Add support for clippituser.tv
+ [qqmusic] Support new URL schemes (#13805)
* [periscope] Renew HLS extraction (#13917)
* [mixcloud] Extract decrypt key

2017.08.13
----------
Core
* [YoutubeDL] Make sure format id is not empty
* [extractor/common] Make _family_friendly_search optional
* [extractor/common] Respect source's type attribute for HTML5 media (#13892)

Extractors
* [pornhub:playlistbase] Skip videos from drop-down menu (#12819, #13902)
+ [fourtube] Add support pornerbros.com (#6022)
+ [fourtube] Add support porntube.com (#7859, #13901)
+ [fourtube] Add support fux.com
* [limelight] Improve embeds detection (#13895)
+ [reddit] Add support for v.redd.it and reddit.com (#13847)
* [aparat] Extract all formats (#13887)
* [mixcloud] Fix play info decryption (#13885)
+ [generic] Add support for vzaar embeds (#13876)

2017.08.09
----------
Core
* [utils] Skip missing params in cli_bool_option (#13865)

Extractors
* [xxxymovies] Fix title extraction (#13868)
+ [nick] Add support for nick.com.pl (#13860)
* [mixcloud] Fix play info decryption (#13867)
* [20min] Fix embeds extraction (#13852)
* [dplayit] Fix extraction (#13851)
+ [niconico] Support videos with multiple formats (#13522)
+ [niconico] Support HTML5-only videos (#13806)

2017.08.06
----------
Core
* Use relative paths for DASH fragments (#12990)

Extractors
* [pluralsight] Fix format selection
- [mpora] Remove extractor (#13826)
+ [voot] Add support for voot.com (#10255, #11644, #11814, #12350, #13218)
* [vlive:channel] Limit number of videos per page to 100 (#13830)
* [podomatic] Extend URL regular expression (#13827)
* [cinchcast] Extend URL regular expression
* [yandexdisk] Relax URL regular expression (#13824)
* [vidme] Extract DASH and HLS formats
- [teamfour] Remove extractor (#13782)
* [pornhd] Fix extraction (#13783)
* [udemy] Fix subtitles extraction (#13812)
* [mlb] Extend URL regular expression (#13740, #13773)
+ [pbs] Add support for new URL schema (#13801)
* [nrktv] Update API host (#13796)

2017.07.30.1
------------
Core
* [downloader/hls] Use redirect URL as manifest base (#13755)
* [options] Correctly hide login info from debug outputs (#13696)

Extractors
+ [watchbox] Add support for watchbox.de (#13739)
- [clipfish] Remove extractor
+ [youjizz] Fix extraction (#13744)
+ [generic] Add support for another ooyala embed pattern (#13727)
+ [ard] Add support for lives (#13771)
* [soundcloud] Update client id
+ [soundcloud:trackstation] Add support for track stations (#13733)
* [svtplay] Use geo verification proxy for API request
* [svtplay] Update API URL (#13767)
+ [yandexdisk] Add support for yadi.sk (#13755)
+ [megaphone] Add support for megaphone.fm
* [amcnetworks] Make rating optional (#12453)
* [cloudy] Fix extraction (#13737)
+ [nickru] Add support for nickelodeon.ru
* [mtv] Improve thumbnal extraction
* [nick] Automate geo-restriction bypass (#13711)
* [niconico] Improve error reporting (#13696)