Log Message:
mpc: update to 0.29.

0.29 (2018/02/11)
* implement %prio% for --format
* the default --format falls back to "performer" if there is no \ 
"artist"
* add command "prio"
* command "outputs" prints attributes
* fix build failure with gcc 7.0 and clang 4.0
* build with Meson instead of autotools