When calling `mrb_equal()` or `mrb_funcall()` family functions, the GC arena should be restored if the loop is repeated by a non-immediate return value.

In my opinion, restoring the GC arena is unnecessary when a non-immediate (true) value causes the function to return (e.g. the `mrb_ary_index_m()` function).

The patch does not take into account the case of recursive calls and may be incomplete.