match-keyword in address match primitive

At the informal Sieve meeting today, we decided to have an address
matching primitive.  I believe that such a primitive should take a match 
keyword argument (:is, :contains, or :matches), and I think that we
meant to say so.

I assume this is the right thing, so I'm going to put it in my notes,
which I'll post real soon now.

-- 
Tim Showalter <tjs+(_at_)andrew(_dot_)cmu(_dot_)edu>