Log Message:
Remove livestreamer, superseded by streamlink

Livestreamer allows watching website streams. It hasn't been actively
developed in a few years, and it doesn't handle stable APIs. It's likely
it has very few remaining working websites.

Superseded by streamlink, a fork of livestreamer under a different name
which is very actively maintained and works for many of the popular
websites.

Announced on pkgsrc-users in 5/sep/2018:
https://mail-index.netbsd.org/pkgsrc-users/2018/09/05/msg027401.html