wrapper.h: move declarations for wrapper.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/diff.c b/diff.c
index 1b0be99..1b0b24c 100644
--- a/diff.c
+++ b/diff.c
@@ -33,6 +33,7 @@
 #include "promisor-remote.h"
 #include "dir.h"
 #include "strmap.h"
+#include "wrapper.h"
 
 #ifdef NO_FAST_WORKING_DIRECTORY
 #define FAST_WORKING_DIRECTORY 0