cache.h: remove dependence on hex.h; make other files include it explicitly

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/entry.c b/entry.c
index 971ab26..c97cfa8 100644
--- a/entry.c
+++ b/entry.c
@@ -2,6 +2,7 @@
 #include "blob.h"
 #include "object-store.h"
 #include "dir.h"
+#include "hex.h"
 #include "streaming.h"
 #include "submodule.h"
 #include "progress.h"