meson.build: require Meson 0.47.2

Meson 0.47.1 suffers from a bug which breaks linking the MPD
executable because the `-lpthread` flag is not propagated from our
`thread.a`.

See https://github.com/mesonbuild/meson/pull/3895

Closes #403

NEWS

@@ -7,6 +7,7 @@ ver 0.21.1 (not yet released)
 * fix build failure on Linux-PowerPC
 * fix build failure on FreeBSD
 * eliminate DLL dependencies on Windows
+* require Meson 0.47.2 because a Meson 0.47.1 bug breaks our build
 
 ver 0.21 (2018/10/31)
 * configuration

doc/user.rst

@@ -54,7 +54,7 @@ Download the source tarball from the `MPD home page <https://musicpd.org>`_ and
 In any case, you need:
 
 * a C++14 compiler (e.g. gcc 6.0 or clang 3.9)
-* `Meson 0.47 <http://mesonbuild.com/>`__ and `Ninja
+* `Meson 0.47.2 <http://mesonbuild.com/>`__ and `Ninja
   <https://ninja-build.org/>`__
 * Boost 1.58
 * pkg-config 

meson.build

@@ -2,7 +2,7 @@ project(
   'mpd',
   ['c', 'cpp'],
   version: '0.21.1',
-  meson_version: '>= 0.47',
+  meson_version: '>= 0.47.2',
   default_options: [
     'c_std=c99',
     'cpp_std=c++14'