Remove global variable "LastRec" in xlog.c

This variable is used only by StartupXLOG() now, so let's make it local
to simplify the code.

Author: Amul Sul
Reviewed-by: Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/CAAJ_b96Qd023itERBRN9Z7P2saNDT3CYvGuMO8RXwndVNN6z7g@mail.gmail.com

Author: michaelpq

src/backend/access/transam/xlog.c

@@ -191,8 +191,6 @@ const struct config_enum_entry recovery_target_action_options[] = {
  */
 CheckpointStatsData CheckpointStats;
 
-static XLogRecPtr LastRec;
-
 /* Local copy of WalRcv->flushedUpto */
 static XLogRecPtr flushedUpto = 0;
 static TimeLineID receiveTLI = 0;
@@ -6679,6 +6677,7 @@ StartupXLOG(void)
 	bool		haveBackupLabel = false;
 	bool		haveTblspcMap = false;
 	XLogRecPtr	RecPtr,
+				LastRec,
 				checkPointLoc,
 				EndOfLog;
 	TimeLineID	EndOfLogTLI;