De-overload configuration file parameter "standby_reconnect_timeout"

Currently the (very generic sounding) "standby_reconnect_timeout" configuration
file parameter is used in several different contexts and it would be useful
to have more granular control over the different timeouts it's used to configure.

This patch introduces "node_rejoin_timeout", used in place of "standby_reconnect_timeout"
(which wasn't documented) when "repmgr node rejoin" is executed, to determine
how long to wait for the node to rejoin the replication cluster.

Additionally "repmgrd_standby_startup_timeout" is introduced as a timeout for
failover situations, when repmgrd executes "repmgr standby follow" to follow
a new primary, and waits for the standby to restart and become available
for connections.

"standby_reconnect_timeout" is now only relevant for "repmgr standby switchover".

Implements GitHub #454.

configfile.h

@@ -102,6 +102,12 @@ typedef struct
 	int			primary_follow_timeout;
 	int			standby_follow_timeout;
 
+	/* standby switchover settings */
+	int			standby_reconnect_timeout;
+
+	/* node rejoin settings */
+	int			node_rejoin_timeout;
+
 	/* node check settings */
 	int			archive_ready_warning;
 	int			archive_ready_critical;
@@ -124,7 +130,7 @@ typedef struct
 	int			degraded_monitoring_timeout;
 	int			async_query_timeout;
 	int			primary_notification_timeout;
-	int			standby_reconnect_timeout;
+	int			repmgrd_standby_startup_timeout;
 
 	/* BDR settings */
 	bool		bdr_local_monitoring_only;
@@ -173,6 +179,10 @@ typedef struct
 		/* standby follow settings */ \
 		DEFAULT_PRIMARY_FOLLOW_TIMEOUT,	\
 		DEFAULT_STANDBY_FOLLOW_TIMEOUT,	\
+		/* standby switchover settings */ \
+		DEFAULT_STANDBY_RECONNECT_TIMEOUT, \
+		/* node rejoin settings */ \
+		DEFAULT_NODE_REJOIN_TIMEOUT, \
 		/* node check settings */ \
 		DEFAULT_ARCHIVE_READY_WARNING, DEFAULT_ARCHIVE_READY_CRITICAL, \
 		DEFAULT_REPLICATION_LAG_WARNING, DEFAULT_REPLICATION_LAG_CRITICAL, \
@@ -186,7 +196,7 @@ typedef struct
         false, -1, \
 		DEFAULT_ASYNC_QUERY_TIMEOUT, \
 		DEFAULT_PRIMARY_NOTIFICATION_TIMEOUT,	\
-		DEFAULT_STANDBY_RECONNECT_TIMEOUT,	\
+		-1,	\
 		/* BDR settings */ \
 		false, DEFAULT_BDR_RECOVERY_TIMEOUT, \
 		/* service settings */ \