Mark DEPRECATED and set EXPIRATION_DATE for 2018-08-01

MusicBrainz Web Service 1.0 support will end on 2018-08-01. There are
currently 2 ports that still depend on this:
audio/kscd
multimedia/gnome-mplayer (non-default option)

See: https://blog.musicbrainz.org/2018/02/01/web-service-ver-1-0-ws-1-will-be-removed-in-6-months/