Modify processing of DECLARE CURSOR and EXPLAIN so that they can resolve the

types of unspecified parameters when submitted via extended query protocol.
This worked in 8.2 but I had broken it during plancache changes.  DECLARE
CURSOR is now treated almost exactly like a plain SELECT through parse
analysis, rewrite, and planning; only just before sending to the executor
do we divert it away to ProcessUtility.  This requires a special-case check
in a number of places, but practically all of them were already special-casing
SELECT INTO, so it's not too ugly.  (Maybe it would be a good idea to merge
the two by treating IntoClause as a form of utility statement?  Not going to
worry about that now, though.)  That approach doesn't work for EXPLAIN,
however, so for that I punted and used a klugy solution of running parse
analysis an extra time if under extended query protocol.

src/backend/optimizer/util/clauses.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.241 2007/04/02 03:49:38 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.242 2007/04/27 22:05:48 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -2945,7 +2945,8 @@ inline_function(Oid funcid, Oid result_type, List *args,
 	 */
 	if (!IsA(querytree, Query) ||
 		querytree->commandType != CMD_SELECT ||
-		querytree->into ||
+		querytree->utilityStmt ||
+		querytree->intoClause ||
 		querytree->hasAggs ||
 		querytree->hasSubLinks ||
 		querytree->rtable ||