csum-file.h: remove unnecessary inclusion of cache.h

With the change in the last commit to move several functions to
write-or-die.h, csum-file.h no longer needs to include cache.h.
However, removing that include forces several other C files, which
directly or indirectly dependend upon csum-file.h's inclusion of
cache.h, to now be more explicit about their dependencies.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit-graph.c

@@ -1,4 +1,4 @@
-#include "git-compat-util.h"
+#include "cache.h"
 #include "config.h"
 #include "gettext.h"
 #include "hex.h"