Bring VRB_Iterate() back to cache.h

In fee476ac VRB_Ignore(), VRB_Cache()
and VRB_Free() were rightly out of vmods' sight.

But VRB_Iterate() is legitemately required for vmods, and including it
in the move seems to be an accident.

bin/varnishd/cache/cache.h

@@ -710,6 +710,11 @@ int ObjGetDouble(struct worker *, struct objcore *, enum obj_attr, double *);
 int ObjGetU32(struct worker *, struct objcore *, enum obj_attr, uint32_t *);
 int ObjGetU64(struct worker *, struct objcore *, enum obj_attr, uint64_t *);
 int ObjCheckFlag(struct worker *, struct objcore *, enum obj_flags of);
+
+/* cache_req_body.c */
+ssize_t VRB_Iterate(struct worker *, struct vsl_log *, struct req *,
+    objiterate_f *func, void *priv);
+
 /* cache_session.c [SES] */
 
 #define SESS_ATTR(UP, low, typ, len)					\

bin/varnishd/cache/cache_varnishd.h

@@ -370,8 +370,6 @@ void Req_AcctLogCharge(struct VSC_main_wrk *, struct req *);
 /* cache_req_body.c */
 int VRB_Ignore(struct req *);
 ssize_t VRB_Cache(struct req *, ssize_t maxsize);
-ssize_t VRB_Iterate(struct worker *, struct vsl_log *, struct req *,
-    objiterate_f *func, void *priv);
 void VRB_Free(struct req *);
 
 /* cache_req_fsm.c [CNT] */