Cause ShutdownPostgres to do a normal transaction abort during backend

exit, instead of trying to take shortcuts.  Introduce some additional
shutdown callback routines to eliminate kluges like having ProcKill
be responsible for shutting down the buffer manager.  Ensure that the
order of operations during shutdown is predictable and what you would
expect given the module layering.

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 1.205 2005/07/04 04:51:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootstrap.c,v 1.206 2005/08/08 03:11:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -378,9 +378,14 @@ BootstrapMain(int argc, char *argv[])
 
 	BaseInit();
 
-	/* needed to get LWLocks */
+	/*
+	 * We aren't going to do the full InitPostgres pushups, but there
+	 * are a couple of things that need to get lit up even in a dummy
+	 * process.
+	 */
 	if (IsUnderPostmaster)
 	{
+		/* set up proc.c to get use of LWLocks */
 		switch (xlogop)
 		{
 			case BS_XLOG_BGWRITER:
@@ -391,6 +396,9 @@ BootstrapMain(int argc, char *argv[])
 				InitDummyProcess(DUMMY_PROC_DEFAULT);
 				break;
 		}
+
+		/* finish setting up bufmgr.c */
+		InitBufferPoolBackend();
 	}
 
 	/*