Prevent "invalid LSN returned from node..." infinite loop

Currently in repmgrd3, if a repmgrd enters failover, but one or more other
repmgrds do not (e.g. partial primary invisibility), the repmgrd in failover
may enter an infinite loop waiting for the repmgrd(s) not in failover to
update shared memory.

dbutils.h

@@ -28,6 +28,8 @@
 #include "strutil.h"
 
 
+#define format_lsn(x) (uint32) (x >> 32), (uint32) x
+
 typedef enum {
 	UNKNOWN = 0,
 	MASTER,
@@ -140,4 +142,9 @@ void        create_checkpoint(PGconn *conn);
 int		    get_node_replication_state(PGconn *conn, char *node_name, char *output);
 t_server_type parse_node_type(const char *type);
 int			get_data_checksum_version(const char *data_directory);
+
+/* backported from repmgr 4.x */
+XLogRecPtr	parse_lsn(const char *str);
+XLogRecPtr	get_last_wal_receive_location(PGconn *conn);
+
 #endif