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/rmgr.h

@@ -1,9 +1,9 @@
 /*
- *
  * rmgr.h
  *
  * Resource managers definition
  *
+ * $Id: rmgr.h,v 1.6 2001/08/25 18:52:42 tgl Exp $
  */
 #ifndef RMGR_H
 #define RMGR_H
@@ -16,6 +16,7 @@ typedef uint8 RmgrId;
 #define RM_XLOG_ID				0
 #define RM_XACT_ID				1
 #define RM_SMGR_ID				2
+#define RM_CLOG_ID				3
 #define RM_HEAP_ID				10
 #define RM_BTREE_ID				11
 #define RM_HASH_ID				12