Replace implementation of pg_log as a relation accessed through the

buffer manager with 'pg_clog', a specialized access method modeled
on pg_xlog.  This simplifies startup (don't need to play games to
open pg_log; among other things, OverrideTransactionSystem goes away),
should improve performance a little, and opens the door to recycling
commit log space by removing no-longer-needed segments of the commit
log.  Actual recycling is not there yet, but I felt I should commit
this part separately since it'd still be useful if we chose not to
do transaction ID wraparound.

src/include/access/xlogutils.h

@@ -6,20 +6,20 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: xlogutils.h,v 1.7 2001/03/22 04:00:32 momjian Exp $
+ * $Id: xlogutils.h,v 1.8 2001/08/25 18:52:42 tgl Exp $
  */
 #ifndef XLOG_UTILS_H
 #define XLOG_UTILS_H
 
 #include "access/rmgr.h"
+#include "storage/buf.h"
+#include "storage/itemptr.h"
 #include "utils/rel.h"
 
 extern int XLogIsOwnerOfTuple(RelFileNode hnode, ItemPointer iptr,
 				   TransactionId xid, CommandId cid);
 extern bool XLogIsValidTuple(RelFileNode hnode, ItemPointer iptr);
 
-extern void XLogOpenLogRelation(void);
-
 extern void XLogInitRelationCache(void);
 extern void XLogCloseRelationCache(void);