Rethink the way FSM truncation works. Instead of WAL-logging FSM

truncations in FSM code, call FreeSpaceMapTruncateRel from smgr_redo. To
make that cleaner from modularity point of view, move the WAL-logging one
level up to RelationTruncate, and move RelationTruncate and all the
related WAL-logging to new src/backend/catalog/storage.c file. Introduce
new RelationCreateStorage and RelationDropStorage functions that are used
instead of calling smgrcreate/smgrscheduleunlink directly. Move the
pending rel deletion stuff from smgrcreate/smgrscheduleunlink to the new
functions. This leaves smgr.c as a thin wrapper around md.c; all the
transactional stuff is now in storage.c.

This will make it easier to add new forks with similar truncation logic,
like the visibility map.

src/backend/access/gin/gininsert.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *			$PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.16 2008/11/13 17:42:09 tgl Exp $
+ *			$PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.17 2008/11/19 10:34:50 heikki Exp $
  *-------------------------------------------------------------------------
  */
 
@@ -284,9 +284,6 @@ ginbuild(PG_FUNCTION_ARGS)
 		elog(ERROR, "index \"%s\" already contains data",
 			 RelationGetRelationName(index));
 
-	/* Initialize FSM */
-	InitIndexFreeSpaceMap(index);
-
 	initGinState(&buildstate.ginstate, index);
 
 	/* initialize the root page */