Log Message:
musicpd: update to 0.21.7.

ver 0.21.7 (2019/04/03)
* input
  - qobuz/tidal: scan tags when loading a playlist
* require Meson 0.49.0 for native libgcrypt-config support
* fix build failure with -Dlocal_socket=false
* Haiku
  - fix build
  - add version info