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/xlog.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: xlog.h,v 1.24 2001/07/19 02:12:35 tgl Exp $
+ * $Id: xlog.h,v 1.25 2001/08/25 18:52:42 tgl Exp $
  */
 #ifndef XLOG_H
 #define XLOG_H
@@ -14,6 +14,7 @@
 #include "access/rmgr.h"
 #include "access/transam.h"
 #include "access/xlogdefs.h"
+#include "storage/bufmgr.h"
 #include "utils/pg_crc.h"