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/optimizer/paths.h

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: paths.h,v 1.54 2001/06/05 17:13:51 tgl Exp $
+ * $Id: paths.h,v 1.55 2001/08/21 16:36:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -36,8 +36,8 @@ extern RelOptInfo *make_fromexpr_rel(Query *root, FromExpr *from);
  *	  routines to generate index paths
  */
 extern void create_index_paths(Query *root, RelOptInfo *rel);
-extern Oid indexable_operator(Expr *clause, Oid opclass, Oid relam,
-				   bool indexkey_on_left);
+extern Oid indexable_operator(Expr *clause, Oid opclass,
+							  bool indexkey_on_left);
 extern List *extract_or_indexqual_conditions(RelOptInfo *rel,
 								IndexOptInfo *index,
 								Expr *orsubclause);