youtube-dl: Update to 20190802

Changes:
20190802
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Extractors
+ [tvigle] Add support for HLS and DASH formats (#21967)
* [tvigle] Fix extraction (#21967)
+ [yandexvideo] Add support for DASH formats (#21971)
* [discovery] Use API call for video data extraction (#21808)
+ [mgtv] Extract format_note (#21881)
* [tvn24] Fix metadata extraction (#21833, #21834)
* [dlive] Relax URL regular expression (#21909)
+ [openload] Add support for oload.best (#21913)
* [youtube] Improve metadata extraction for age gate content (#21943)

(leot)