Log Message:
musicpd: update to 0.20.20.

ver 0.20.20 (2018/05/22)
* protocol
  - fix "modified-since" filter regression
* output
  - pulse: cork stream when paused due to "single" mode
* decoder
  - dsdiff, dsf: support more MIME types
  - dsdiff, dsf: allow 4 MB ID3 tags
  - opus: support R128_ALBUM_GAIN tag
* Android, Windows
  - enable the "proxy" database plugin