pass "struct client" to dbUtils.c, song.c, tag_print.c

Don't pass the raw file descriptor around.  This migration patch is
rather large, because all of the sources have inter dependencies - we
have to change all of them at the same time.

src/directory.h

@@ -55,7 +55,7 @@ void closeMp3Directory(void);
 
 int isRootDirectory(const char *name);
 
-int printDirectoryInfo(int fd, const char *dirname);
+int printDirectoryInfo(struct client *client, const char *dirname);
 
 int checkDirectoryDB(void);