New port multimedia/streamlink 1.4.1.

Streamlink is a command-line utility that pipes video streams from various
services into a video player, such as VLC.

The main purpose of Streamlink is to allow the user to avoid buggy and CPU
heavy flash plugins but still be able to enjoy various streamed content.

There is also an API available for developers who want access to the video
stream data.

This project was forked from Livestreamer, which is no longer maintained.

WWW: https://streamlink.github.io/

Over the original submission, add these changes:

• limit to Python 3.5+ because 241566 was lacking the four requisites (one not even in the ports tree before) needed additionally on 2.7, and upstream deprecated Python 2.7 support
• add support for make test (TEST_DEPENDS=, do-test:)
• add a PYCOUNTRY port option with a "magic" default that will be enabled while textproc/py-iso3166 (new -> Bugzilla #241565) is missing and use py-country instead of py-iso-639 and py-iso3166. So this port no longer depends on PR 241565.

PR: 241566
Submitted by: takefu@airport.fm (new maintainer)