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/command.h

@@ -19,19 +19,15 @@
 #ifndef COMMAND_H
 #define COMMAND_H
 
-#include "../config.h"
-
-#include "list.h"
-#include "myfprintf.h"
-#include "log.h"
-#include "ack.h"
-#include "sllist.h"
+#include "gcc.h"
 #include "os_compat.h"
 
 #define COMMAND_RETURN_KILL	10
 #define COMMAND_RETURN_CLOSE	20
 #define COMMAND_MASTER_READY	30
 
+struct strnode;
+
 int processListOfCommands(int fd, int *permission, int *expired,
 			  int listOK, struct strnode *list);