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/tag_print.h

@@ -20,9 +20,10 @@
 #define TAG_PRINT_H
 
 struct tag;
+struct client;
 
-void tag_print_types(int fd);
+void tag_print_types(struct client *client);
 
-void tag_print(int fd, const struct tag *tag);
+void tag_print(struct client *client, const struct tag *tag);
 
 #endif