fix for -fno-common
https://gitweb.gentoo.org/repo/gentoo.git/commit/media-sound/scmpc/files?id=c9f42ac8feb314f3f2f6ec7cfd8c535ff33fe735

Index: src/preferences.h
--- src/preferences.h.orig
+++ src/preferences.h
@@ -32,7 +32,7 @@
 /**
  * scmpc settings
  */
-struct {
+struct prefs_t {
 	gchar *mpd_hostname;
 	gushort mpd_port;
 	gushort mpd_timeout;
@@ -48,7 +48,9 @@ struct {
 	gchar *cache_file;
 	guint queue_length;
 	guint cache_interval;
-} prefs;
+};
+
+extern struct prefs_t prefs;
 
 /**
  * Initialize preferences