Log Message:
Updated libmpdclient to 2.13.

Switch to meson build framework since autoconf one was removed.

libmpdclient 2.13 (2017/07/25)
* fix build with meson > 0.38.1
* fix connect error "Operation now in progress"

libmpdclient 2.12 (2017/07/21)
* support MPD protocol 0.21
  - support tag "OriginalDate"
  - command "tagtypes" plus "disable", "enable", \ 
"clear"
* support MPD protocol 0.20
  - support "plchanges" and "plchangesposid" with range
* support MPD protocol 0.19
  - commands "addtagid", "cleartagid"
  - command "listfiles"
  - grouping for "list" and "count"
  - tag "AlbumSort"
  - "seekid" with float time
* use relative #include paths to avoid clashes with other libmpdclient copies
* build with Meson instead of autotools