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>
diff --git a/dir.c b/dir.c
index d1f1b1e..aa84099 100644
--- a/dir.c
+++ b/dir.c
@@ -13,6 +13,7 @@
 #include "dir.h"
 #include "environment.h"
 #include "gettext.h"
+#include "object-file.h"
 #include "object-store.h"
 #include "attr.h"
 #include "refs.h"