Recursive Alias Declaration under MSVC

To my understanding `safe<>` should work in any template as integer safety is orthogonal.

I am unable to use `safe` in `std::span` in MSVC:

```c++
#include
#include
#include

using Int = boost::safe_numerics::safe;

auto foo_safe(std::span numbers) -> int {
return int {numbers[0]};
}

int main() {
const auto numbers = std::vector {
Int {1}, Int {2}, Int {3}
};

return foo_safe(numbers);
}

```

This leads to a **recursive alias declaration** error:
```
error C2968:
'legal_overload > > > >,__int64>':
recursive alias declaration
```

[See on godbolt.](https://godbolt.org/z/831ThMsP1)