PATCH to libstdc++ to use __cxa_thread_atexit_impl if available

[Jakub Jelinek]

On Sat, Jan 19, 2013 at 12:22:23PM -0500, Jason Merrill wrote:
> Siddhesh has a patch to implement the thread atexit functionality in
> glibc in order to integrate better with the dynamic loader and run
> the cleanups in the correct order.  Once it's available there, this
> patch will make the copy in libsupc++ use it.  The main
> __cxa_thread_atexit function will always live in libsupc++, however,
> in order to maintain ABI compatibility between releases of
> libstdc++.
> 
> Does this configure change look right, or should it go in linkage.m4
> somewhere?
> 
> I think I'll hold off checking this in until Siddhesh's patch goes
> into glibc.

Yeah, it should make it into glibc first (no idea why is it taking so long),
otherwise we can't be sure it won't be implemented differently in glibc.

	Jakub