Remove another unused include file with obsolete, useless,

confusing definitions in it.

src/include/storage/pagenum.h

-/*-------------------------------------------------------------------------
- *
- * pagenum.h
- *	  POSTGRES page number definitions.
- *
- *
- * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- * $Id: pagenum.h,v 1.10 2001/01/24 19:43:28 momjian Exp $
- *
- *-------------------------------------------------------------------------
- */
-#ifndef PAGENUM_H
-#define PAGENUM_H
-
-
-typedef uint16 PageNumber;
-
-typedef uint32 LogicalPageNumber;
-
-#define InvalidLogicalPageNumber		0
-
-/*
- * LogicalPageNumberIsValid
- *		True iff the logical page number is valid.
- */
-#define LogicalPageNumberIsValid(pageNumber) \
-	((bool)((pageNumber) != InvalidLogicalPageNumber))
-
-
-#endif	 /* PAGENUM_H */