object-name.h: move declarations for object-name.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/bisect.c b/bisect.c
index 0a5f2ed..e708e8b 100644
--- a/bisect.c
+++ b/bisect.c
@@ -17,6 +17,7 @@
 #include "strvec.h"
 #include "commit-slab.h"
 #include "commit-reach.h"
+#include "object-name.h"
 #include "object-store.h"
 #include "dir.h"