Commented Unassigned: defect in lazy initialization of static in windows_category() [391]

The instance object in the code below races on construction during multi-threaded use of the API when generating errors. The generated code on Windows/VS2013 is not thread safe. The actual error is generated in (http_client_winhttp.cpp) build_error_message while trying to access the object via windows_category(). I have not created a minimal reproduction scenario...

Simple fix, call the function somewhere safe (i.e. single threaded) to instantiate the object:
```c++
utility::details::windows_category();
```

```c++
const std::error_category & __cdecl windows_category()
{
static details::windows_category_impl instance;
return instance;
}
```

another:

```c++
const web::json::details::json_error_category_impl& web::json::details::json_error_category()
{
static web::json::details::json_error_category_impl instance;
return instance;
}
```
Comments: by fix, I mean workaround...