object-file.h: move declarations for object-file.c functions from cache.h

Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/update-index.c

@@ -15,6 +15,7 @@
 #include "cache-tree.h"
 #include "tree-walk.h"
 #include "builtin.h"
+#include "object-file.h"
 #include "refs.h"
 #include "resolve-undo.h"
 #include "parse-options.h"