Fix heap_page_prune() parameter order confusion introduced in dc7420c2.

Both luckily and unluckily the passed values meant the same for all
types. Luckily because that meant my confusion caused no harm,
unluckily because otherwise the compiler might have warned...

In passing, synchronize parameter names between definition and
declaration.
Reported-By: Peter Geoghegan <pg@bowt.ie>
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CAH2-Wz=L=nBoepQdH9b5Qd0nMvepFT2CnT6sjWvvpOXa=K8HVQ@mail.gmail.com

src/backend/access/heap/vacuumlazy.c

@@ -1237,8 +1237,8 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
 		 * We count tuples removed by the pruning step as removed by VACUUM
 		 * (existing LP_DEAD line pointers don't count).
 		 */
-		tups_vacuumed += heap_page_prune(onerel, buf, vistest, false,
-										 InvalidTransactionId, 0,
+		tups_vacuumed += heap_page_prune(onerel, buf, vistest,
+										 InvalidTransactionId, 0, false,
 										 &vacrelstats->latestRemovedXid,
 										 &vacrelstats->offnum);
 

src/include/access/heapam.h

@@ -174,8 +174,8 @@ struct GlobalVisState;
 extern void heap_page_prune_opt(Relation relation, Buffer buffer);
 extern int	heap_page_prune(Relation relation, Buffer buffer,
 							struct GlobalVisState *vistest,
-							TransactionId limited_oldest_xmin,
-							TimestampTz limited_oldest_ts,
+							TransactionId old_snap_xmin,
+							TimestampTz old_snap_ts_ts,
 							bool report_stats, TransactionId *latestRemovedXid,
 							OffsetNumber *off_loc);
 extern void heap_page_prune_execute(Buffer buffer,