[c++0x] std::thread fixes

[Paolo Carlini]

Jonathan Wakely wrote:
> As discussed recently, the names in std::thread don't follow the
> libstdc++ coding style.
>
> There's a memory leak in the case where a new thread can't be started,
> because of the shared_ptr cycle created in _M_this_ptr.
>
> The std::thread move constructor and assignment operator definitions
> are missing.
>
>  _Thread_data_base doesn't need a mutex, and doesn't need to derive
> from enable_shared_from_this.
>   
[snip]

Thanks Jon for this work. I understand it also includes changes in ABI,
because of the mutexes, thus, even if we are talking about C++0x mode,
it would be nice to converge as soon as possible and then do not make
changes during 4.4.x. I'd like to hear Chris too, about std::thread...

Paolo.