Make printf safe

[Nick Treleaven]

On Thursday, 18 July 2024 at 16:45:02 UTC, Nick Treleaven wrote:
> ```d
> pragma(msg, printf) printf(const char* fmt, ...) @safe;
> ```

I messed that up:

```d
pragma(printf) extern(C) int printf(const char* fmt, ...) @safe;
```