[libcxx-commits] [libcxx] [libc++] Make `_Atomic(T)` directly use an alias template (PR #168679)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

Looking at https://eel.is/c++draft/stdatomic.h.syn#1 right now, it clearly says:

```
template<class T>
  using std-atomic = std::atomic<T>;        // exposition only

#define _Atomic(T) std-atomic<T>
```

I think this is pedantic but clearly correct. If the Standard wants us to do differently, they can say it, but right now we are accepting code that is technically invalid.

https://github.com/llvm/llvm-project/pull/168679