Fix outfuncs.c to dump A_Const nodes representing NULLs correctly. This has

been broken since forever, but was not noticed because people seldom look
at raw parse trees.  AFAIK, no impact on users except that debug_print_parse
might fail; but patch it all the way back anyway.  Per report from Jeff Ross.

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.311 2007/06/11 22:22:40 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.312 2007/07/17 01:21:43 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -1900,6 +1900,10 @@ _outValue(StringInfo str, Value *value)
 			/* internal representation already has leading 'b' */
 			appendStringInfoString(str, value->val.str);
 			break;
+		case T_Null:
+			/* this is seen only within A_Const, not in transformed trees */
+			appendStringInfoString(str, "NULL");
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d", (int) value->type);
 			break;