BUG #5915: OldSerXidAdd inflates pg_serial too much

The following bug has been logged online:

Bug reference:      5915
Logged by:          YAMAMOTO Takashi
Email address:      yamt@mwd.biglobe.ne.jp
PostgreSQL version: 9.1devel
Operating system:   NetBSD
Description:        OldSerXidAdd inflates pg_serial too much
Details:

a seemingly wrong math in OldSerXidAdd makes it busy writing zeros
to pg_serial.


diff --git a/src/backend/storage/lmgr/predicate.c
b/src/backend/storage/lmgr/predicate.c
index aa657fa..297508b 100644
--- a/src/backend/storage/lmgr/predicate.c
+++ b/src/backend/storage/lmgr/predicate.c
@@ -755,7 +755,7 @@ OldSerXidAdd(TransactionId xid, SerCommitSeqNo
minConflictCommitSeqNo)
     {
         page = OldSerXidPage(tailXid);
         oldSerXidControl->tailSegment = OldSerXidSegment(page);
-        page = oldSerXidControl->tailSegment * OLDSERXID_ENTRIESPERPAGE;
+        page = oldSerXidControl->tailSegment * SLRU_PAGES_PER_SEGMENT;
         isNewPage = true;
     }
     else