notmuch 0.18.1
notmuch: add 0.18.1 bottle.
Update ncmpc to 0.23

This is a bug-fix release. 0.22 was broken due to missing Po files for
i10n builds. Note that dependencies to other libraries have changed a
bit:
- libmpdclient >= 2.3 required
- MPD >= 0.16 required
ncmpc: add 0.23 bottle.