Centralize implementation of delay code by creating a pg_usleep()

subroutine in src/port/pgsleep.c.  Remove platform dependencies from
miscadmin.h and put them in port.h where they belong.  Extend recent
vacuum cost-based-delay patch to apply to VACUUM FULL, ANALYZE, and
non-btree index vacuuming.

By the way, where is the documentation for the cost-based-delay patch?

src/backend/access/hash/hash.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.70 2004/01/07 18:56:23 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.71 2004/02/10 03:42:43 tgl Exp $
  *
  * NOTES
  *	  This file contains only the public interface routines.
@@ -23,6 +23,7 @@
 #include "access/heapam.h"
 #include "access/xlogutils.h"
 #include "catalog/index.h"
+#include "commands/vacuum.h"
 #include "executor/executor.h"
 #include "miscadmin.h"
 
@@ -514,6 +515,8 @@ loop_top:
 			OffsetNumber maxoffno;
 			bool		page_dirty = false;
 
+			vacuum_delay_point();
+
 			buf = _hash_getbuf(rel, blkno, HASH_WRITE);
 			page = BufferGetPage(buf);
 			_hash_checkpage(rel, page, LH_BUCKET_PAGE | LH_OVERFLOW_PAGE);