Change internal integer representation of Value node

A Value node would store an integer as a long.  This causes needless
portability risks, as long can be of varying sizes.  Change it to use
int instead.  All code using this was already careful to only store
32-bit values anyway.

Reviewed-by: Michael Paquier <michael@paquier.xyz>

src/backend/utils/misc/guc.c

@@ -6913,7 +6913,7 @@ flatten_set_variable_args(const char *name, List *args)
 		switch (nodeTag(&con->val))
 		{
 			case T_Integer:
-				appendStringInfo(&buf, "%ld", intVal(&con->val));
+				appendStringInfo(&buf, "%d", intVal(&con->val));
 				break;
 			case T_Float:
 				/* represented as a string, so just copy it */