Demote variable from global to local

recoveryDelayUntilTime was introduced by commit 36da3cfb45 as a global
because its method of operation was devilishly intrincate.  Commit
c945af80cf removed all that complexity and could have turned it into a
local variable, but didn't.  Do so now.

Discussion: https://postgr.es/m/20191213200751.GA10731@alvherre.pgsql
Reviewed-by: Michaël Paquier, Daniel Gustafsson

src/backend/access/transam/xlog.c

@@ -277,7 +277,6 @@ static TimestampTz recoveryTargetTime;
 const char *recoveryTargetName;
 XLogRecPtr	recoveryTargetLSN;
 int			recovery_min_apply_delay = 0;
-TimestampTz recoveryDelayUntilTime;
 
 /* options formerly taken from recovery.conf for XLOG streaming */
 bool		StandbyModeRequested = false;
@@ -5970,6 +5969,7 @@ recoveryApplyDelay(XLogReaderState *record)
 {
 	uint8		xact_info;
 	TimestampTz xtime;
+	TimestampTz	delayUntil;
 	long		secs;
 	int			microsecs;
 
@@ -6005,15 +6005,13 @@ recoveryApplyDelay(XLogReaderState *record)
 	if (!getRecordTimestamp(record, &xtime))
 		return false;
 
-	recoveryDelayUntilTime =
+	delayUntil = TimestampTzPlusMilliseconds(xtime, recovery_min_apply_delay);
-		TimestampTzPlusMilliseconds(xtime, recovery_min_apply_delay);
 
 	/*
 	 * Exit without arming the latch if it's already past time to apply this
 	 * record
 	 */
-	TimestampDifference(GetCurrentTimestamp(), recoveryDelayUntilTime,
+	TimestampDifference(GetCurrentTimestamp(), delayUntil, &secs, &microsecs);
-						&secs, &microsecs);
 	if (secs <= 0 && microsecs <= 0)
 		return false;
 
@@ -6028,10 +6026,9 @@ recoveryApplyDelay(XLogReaderState *record)
 			break;
 
 		/*
-		 * Wait for difference between GetCurrentTimestamp() and
+		 * Wait for difference between GetCurrentTimestamp() and delayUntil
-		 * recoveryDelayUntilTime
 		 */
-		TimestampDifference(GetCurrentTimestamp(), recoveryDelayUntilTime,
+		TimestampDifference(GetCurrentTimestamp(), delayUntil,
 							&secs, &microsecs);
 
 		/*