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/tagTracker.h

@@ -19,8 +19,6 @@
 #ifndef TAG_TRACKER_H
 #define TAG_TRACKER_H
 
-#include "tag.h"
-
 char *getTagItemString(int type, char *string);
 
 void removeTagItemString(int type, char *string);