[ietf-dkim] Nits with section 2 Language and Terminology

[Arvel Hathcock]

> The "and how that domain signs" might be a little confusing.  
> How a subject signs their email might be interpreted as something 
> like "the domain always signs the Subject header field" and I 
> think we decided not to do that.  How about instead "which includes 
> information on whether that domain signs their email and related 
> information."  Less specific, but less confusing IMO.

Fine by me, thanks!

Arvel