Making emplaceRef public

[Seb]

On Friday, 6 April 2018 at 17:46:26 UTC, Per Nordlöw wrote:
> Why isn't `std.conv.emplaceRef` public when `std.conv.emplace` 
> is?
>
> AFAICT,
>
> emplaceRef(x, ...)
>
> is a bit more @safe than
>
> emplace(&x, ...)
>
> ...

I had the same thoughts too:

https://issues.dlang.org/show_bug.cgi?id=18701

We can even do this without introducing a new symbol, but simply 
let emplace accept pointers and ref like we need with 
formattedRead for nice backwards compatibility.