update prolog_parser to v0.8.33

src/prolog/lib/builtins.pl

@@ -48,7 +48,7 @@ expand_op_list([Op | OtherOps], Pred, Spec, [(:- op(Pred, Spec, Op)) | OtherResu
 :- op(700, xfx, [==, \==, @=<, @>=, @<, @>]).
 
 % the maximum arity flag. needs to be replaced with current_prolog_flag(max_arity, MAX_ARITY).
-max_arity(63).
+max_arity(255).
 
 % conditional operators.
 :- op(1050, xfy, ->).

src/prolog/machine/machine_state_impl.rs

@@ -3416,7 +3416,7 @@ impl MachineState {
         self.mode = MachineMode::Write;
         self.and_stack.clear();
         self.or_stack.clear();
-        self.registers = vec![Addr::HeapCell(0); 64];
+        self.registers = vec![Addr::HeapCell(0); MAX_ARITY + 1]; // self.registers[0] is never used.
         self.block = 0;
 
         self.ball.reset();