[patch] Fix BZ#20544 (assert function passed to atexit/on_exit/__cxa_atexit != NULL)

[Florian Weimer]

* Paul Pluzhnikov:

> On Thu, Nov 29, 2018 at 7:06 AM Florian Weimer <fweimer@redhat.com> wrote:
>
>> Perhaps:
>>
>>     stdlib: assert on NULL function pointer in atexit etc. [BZ #20544]
>
> Thanks. Revised patch attached.

I think this version is okay.

Thanks,
Florian