audio/musicpc: update to 0.34

ChangeLog: https://raw.githubusercontent.com/MusicPlayerDaemon/mpc/v0.34/NEWS

• add commands "albumart", "readpicture"
• don't print status after error
• custom status format
• support grouping "list" results
• meson: auto-build libmpdclient if not available
• require libmpdclient 2.16 or newer
• require MPD 0.21 or newer

PR: 263938
Reported by: uzsolt@uzsolt.hu (maintainer)