setup.h: move declarations for setup.c functions from cache.h

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 5541e76..73b6e58 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -23,6 +23,7 @@
 #include "resolve-undo.h"
 #include "revision.h"
 #include "run-command.h"
+#include "setup.h"
 #include "submodule.h"
 #include "submodule-config.h"
 #include "tree.h"