Restructure pg_opclass, pg_amop, and pg_amproc per previous discussions in

pgsql-hackers.  pg_opclass now has a row for each opclass supported by each
index AM, not a row for each opclass name.  This allows pg_opclass to show
directly whether an AM supports an opclass, and furthermore makes it possible
to store additional information about an opclass that might be AM-dependent.
pg_opclass and pg_amop now store "lossy" and "haskeytype" information that we
previously expected the user to remember to provide in CREATE INDEX commands.
Lossiness is no longer an index-level property, but is associated with the
use of a particular operator in a particular index opclass.

Along the way, IndexSupportInitialize now uses the syscaches to retrieve
pg_amop and pg_amproc entries.  I find this reduces backend launch time by
about ten percent, at the cost of a couple more special cases in catcache.c's
IndexScanOK.

Initial work by Oleg Bartunov and Teodor Sigaev, further hacking by Tom Lane.

initdb forced.

src/include/nodes/parsenodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: parsenodes.h,v 1.141 2001/08/16 20:38:55 tgl Exp $
+ * $Id: parsenodes.h,v 1.142 2001/08/21 16:36:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -500,7 +500,6 @@ typedef struct IndexStmt
 	char	   *relname;		/* name of relation to index on */
 	char	   *accessMethod;	/* name of access method (eg. btree) */
 	List	   *indexParams;	/* a list of IndexElem */
-	List	   *withClause;		/* a list of DefElem */
 	Node	   *whereClause;	/* qualification (partial-index predicate) */
 	List	   *rangetable;		/* range table for qual, filled in by
 								 * transformStmt() */