fix for -fno-common
https://svnweb.freebsd.org/changeset/ports/546834

Index: src/mpd_client.c
--- src/mpd_client.c.orig
+++ src/mpd_client.c
@@ -27,6 +27,8 @@
 #include "config.h"
 #include "json_encode.h"
 
+struct t_mpd mpd;
+
 /* forward declaration */
 static int mpd_notify_callback(struct mg_connection *c, enum mg_event ev);