Infrastructure for deducing Param types from context, in the same way

that the types of untyped string-literal constants are deduced (ie,
when coerce_type is applied to 'em, that's what the type must be).
Remove the ancient hack of storing the input Param-types array as a
global variable, and put the info into ParseState instead.  This touches
a lot of files because of adjustment of routine parameter lists, but
it's really not a large patch.  Note: PREPARE statement still insists on
exact specification of parameter types, but that could easily be relaxed
now, if we wanted to do so.

src/include/parser/gramparse.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: gramparse.h,v 1.26 2003/04/27 20:09:44 tgl Exp $
+ * $Id: gramparse.h,v 1.27 2003/04/29 22:13:11 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -17,9 +17,8 @@
 
 #include "nodes/parsenodes.h"
 
+
 /* from parser.c */
-extern void parser_param_set(Oid *typev, int nargs);
-extern Oid	param_type(int t);
 extern int	yylex(void);
 
 /* from scan.l */