Move AllowCascadeReplication() define from xlog.h to replication include

file.

Per suggestion from Alvaro.

src/include/replication/walreceiver.h

@@ -12,6 +12,7 @@
 #ifndef _WALRECEIVER_H
 #define _WALRECEIVER_H
 
+#include "access/xlog.h"
 #include "access/xlogdefs.h"
 #include "storage/spin.h"
 #include "pgtime.h"
@@ -27,6 +28,9 @@ extern bool hot_standby_feedback;
  */
 #define MAXCONNINFO		1024
 
+/* Can we allow the standby to accept replication connection from another standby? */
+#define AllowCascadeReplication() (EnableHotStandby && max_wal_senders > 0)
+
 /*
  * Values for WalRcv->walRcvState.
  */

src/include/replication/walsender.h

@@ -13,6 +13,7 @@
 #define _WALSENDER_H
 
 #include "access/xlog.h"
+#include "fmgr.h"
 #include "nodes/nodes.h"
 #include "storage/latch.h"
 #include "replication/syncrep.h"