Interpolation struct names and location

[Paul Backus]

On Wednesday, 14 February 2024 at 16:28:32 UTC, Steven 
Schveighoffer wrote:
> I thought of `IHeader` but that looks like an interface...
>
> I also thought of `IESHeader` but this is less obvious to 
> someone who sees it.
>
> InterpHeader is still long, but a bit better. Any reduction is 
> better than no reduction?

`IstrHeader` or `IseqHeader`, maybe? Shaves off a couple more 
characters.