MFH: r461531

multimedia/mpv: Update to 0.27.1

Changelog: https://github.com/mpv-player/mpv/releases/tag/v0.27.1

Security: https://vuxml.freebsd.org/freebsd/3ee6e521-0d32-11e8-99b0-d017c2987f9a.html

Approved by: ports-secteam (riggs)