The old setup relied on there being at least one constructor *or* the
value of *__CTOR_LIST__ being NULL. Neither of these are guaranteed; and
having no C++ constructors actually resulted in a random value being
read (which passed the NULL check!). This new setup uses the
__CTOR_END__ symbol; which is a pointer to just after the end of the
list. When there are no constructors, it has the same value as
__CTOR_LIST__; so the while loop is never entered.
This fix also allows us to re-enable destructors; in case they're ever
needed.
26a006cfac