clean up CPP includes

Try to only include headers which are really needed.  We should
particularly check all "headers including other headers".  The
long-term goal is to have a manageable, small API for plugins
(decoders, output) without so many mpd internals cluttering the
namespace.

git-svn-id: https://svn.musicpd.org/mpd/trunk@7319 09075e82-0dd4-0310-85a5-a0d7c8717e4f

src/inputPlugins/wavpack_plugin.c

@@ -29,6 +29,7 @@
 #include "../playerData.h"
 #include "../outputBuffer.h"
 #include "../os_compat.h"
+#include "../path.h"
 
 #include <wavpack/wavpack.h>