[PATCH, v3] std::thread ctor passes function pointer by reference to _M_make_shared_data.

[Benjamin Kosnik]

> By explicitly specifying the template argument to the
> _M_make_shared_data call, pointers are passed by value and
> rvalue/lvalue-refs are still forwarded correctly.
> 
> Tested x86_64, ok for trunk?

OK, thanks.

-benjamin