Fix up the remaining places where the expression node structure would lose

available information about the typmod of an expression; namely, Const,
ArrayRef, ArrayExpr, and EXPR and ARRAY SubLinks.  In the ArrayExpr and
SubLink cases it wasn't really the data structure's fault, but exprTypmod()
being lazy.  This seems like a good idea in view of the expected increase in
typmod usage from Teodor's work to allow user-defined types to have typmods.
In particular this responds to the concerns we had about eliminating the
special-purpose hack that exprTypmod() used to have for BPCHAR Consts.
We can now tell whether or not such a Const has been cast to a specific
length, and report or display properly if so.

initdb forced due to changes in stored rules.

src/backend/optimizer/prep/preptlist.c

@@ -16,7 +16,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/preptlist.c,v 1.86 2007/02/19 07:03:30 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/preptlist.c,v 1.87 2007/03/17 00:11:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -281,6 +281,7 @@ expand_targetlist(List *tlist, int command_type,
 					if (!att_tup->attisdropped)
 					{
 						new_expr = (Node *) makeConst(atttype,
+													  -1,
 													  att_tup->attlen,
 													  (Datum) 0,
 													  true,		/* isnull */
@@ -296,6 +297,7 @@ expand_targetlist(List *tlist, int command_type,
 					{
 						/* Insert NULL for dropped column */
 						new_expr = (Node *) makeConst(INT4OID,
+													  -1,
 													  sizeof(int32),
 													  (Datum) 0,
 													  true,		/* isnull */
@@ -315,6 +317,7 @@ expand_targetlist(List *tlist, int command_type,
 					{
 						/* Insert NULL for dropped column */
 						new_expr = (Node *) makeConst(INT4OID,
+													  -1,
 													  sizeof(int32),
 													  (Datum) 0,
 													  true,		/* isnull */