Restructure smgr API as per recent proposal. smgr no longer depends on

the relcache, and so the notion of 'blind write' is gone.  This should
improve efficiency in bgwriter and background checkpoint processes.
Internal restructuring in md.c to remove the not-very-useful array of
MdfdVec objects --- might as well just use pointers.
Also remove the long-dead 'persistent main memory' storage manager (mm.c),
since it seems quite unlikely to ever get resurrected.

src/backend/bootstrap/bootstrap.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootstrap.c,v 1.175 2004/01/07 18:56:25 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootstrap.c,v 1.176 2004/02/10 01:55:24 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -465,14 +465,12 @@ BootstrapMain(int argc, char *argv[])
 			break;
 
 		case BS_XLOG_CHECKPOINT:
-			CreateDummyCaches();
 			CreateCheckPoint(false, false);
 			SetSavedRedoRecPtr();		/* pass redo ptr back to
 										 * postmaster */
 			proc_exit(0);		/* done */
 
 		case BS_XLOG_BGWRITER:
-			CreateDummyCaches();
 			BufferBackgroundWriter();
 			proc_exit(0);		/* done */