Restructure representation of aggregate functions so that they have pg_proc

entries, per pghackers discussion.  This fixes aggregates to live in
namespaces, and also simplifies/speeds up lookup in parse_func.c.
Also, add a 'proimplicit' flag to pg_proc that controls whether a type
coercion function may be invoked implicitly, or only explicitly.  The
current settings of these flags are more permissive than I would like,
but we will need to debate and refine the behavior; for now, I avoided
breaking regression tests as much as I could.

src/backend/utils/adt/sets.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/Attic/sets.c,v 1.42 2002/04/05 00:31:29 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/Attic/sets.c,v 1.43 2002/04/11 20:00:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -58,16 +58,19 @@ SetDefine(char *querystr, Oid elemType)
 							 true,		/* returnsSet */
 							 elemType,	/* returnType */
 							 SQLlanguageId,	/* language */
-							 querystr,	/* sourceCode */
-							 fileName,	/* fileName */
+							 querystr,	/* prosrc */
+							 fileName,	/* probin */
+							 false,		/* not aggregate */
 							 true,		/* trusted */
+							 false,		/* not implicit coercion */
 							 false,		/* isStrict (irrelevant, no args) */
 							 PROVOLATILE_VOLATILE,	/* assume unsafe */
 							 100,		/* byte_pct */
 							 0, /* perbyte_cpu */
 							 0, /* percall_cpu */
 							 100,		/* outin_ratio */
-							 NIL);		/* argList */
+							 0,			/* parameterCount */
+							 NULL);		/* parameterTypes */
 
 	/*
 	 * Since we're still inside this command of the transaction, we can't