Report the unexpected token for P_UNEXPECTED_TOKEN returns - close #11

spec/test_error_positions.d

@@ -17,11 +17,13 @@ unittest
     p_context_init(&context, input);
     assert(p_parse(&context) == P_UNEXPECTED_TOKEN);
     assert(p_position(&context) == p_position_t(2, 3));
+    assert(context.token == TOKEN_a);
 
     input = "12";
     p_context_init(&context, input);
     assert(p_parse(&context) == P_UNEXPECTED_TOKEN);
     assert(p_position(&context) == p_position_t(0, 0));
+    assert(context.token == TOKEN_num);
 
     input = "a 12\n\nab";
     p_context_init(&context, input);

spec/test_parser_rule_from_multiple_states.d

@@ -13,6 +13,7 @@ unittest
     p_context_init(&context, input);
     assert(p_parse(&context) == P_UNEXPECTED_TOKEN);
     assert(p_position(&context) == p_position_t(0, 1));
+    assert(context.token == TOKEN___EOF);
 
     input = "a b";
     p_context_init(&context, input);