std::call_once without TLS

[Jonathan Wakely]

2009/4/26 Jonathan Wakely:
>
> The code is very broken, the only way I can see to fix it while still
> returning a reference to a unique_lock will be to use
> pthread_set_specific instead of TLS.
>

I've created libstdc++/39909 to track this.  I don't care about the
non-TLS implementation, since TLS works on all the platforms I use, so
I'll come back to this another time.