Log Message:
youtube-dl: Update to 20190608

Changes:
2019.06.08
----------
Core
* [downloader/common] Improve rate limit (#21301)
* [utils] Improve strip_or_none
* [extractor/common] Strip src attribute for HTML5 entries code (#18485,
  #21169)

Extractors
* [ted] Fix playlist extraction (#20844, #21032)
* [vlive:playlist] Fix video extraction when no playlist is found (#20590)
+ [vlive] Add CH+ support (#16887, #21209)
+ [openload] Add support for oload.website (#21329)
+ [tvnow] Extract HD formats (#21201)
+ [redbulltv] Add support for rrn:content URLs (#21297)
* [youtube] Fix average rating extraction (#21304)
+ [bitchute] Extract HTML5 formats (#21306)
* [cbsnews] Fix extraction (#9659, #15397)
* [vvvvid] Relax URL regular expression (#21299)
+ [prosiebensat1] Add support for new API (#21272)
+ [vrv] Extract adaptive_hls formats (#21243)
* [viki] Switch to HTTPS (#21001)
* [LiveLeak] Check if the original videos exist (#21206, #21208)
* [rtp] Fix extraction (#15099)
* [youtube] Improve DRM protected videos detection (#1774)
+ [srgssrplay] Add support for popupvideoplayer URLs (#21155)
+ [24video] Add support for porno.24video.net (#21194)
+ [24video] Add support for 24video.site (#21193)
- [pornflip] Remove extractor
- [criterion] Remove extractor (#21195)
* [pornhub] Use HTTPS (#21061)
* [bitchute] Fix uploader extraction (#21076)
* [streamcloud] Reduce waiting time to 6 seconds (#21092)
- [novamov] Remove extractors (#21077)
+ [openload] Add support for oload.press (#21135)
* [vivo] Fix extraction (#18906, #19217)