#11 allow caller of fetch_author_policy() to specify domain

[Jason Long]

3. allow caller of fetch_author_policy() to explicitly specify a
domain (or an author's e-mail address) to be queried for a policy;

> [...] parsing the author address
> in a From header field - amavisd-new does it very carefully,
> following RFC 2822 syntax closely, including dealing with nested
> comments, and other horrors. The Mail::DKIM just uses a simpleminded
> Mail::Address, which sometimes gets it wrong. I could use an API
> where the caller could tell the verifier what is the author's address.
> Perhaps the fetch_author_policy() could take an optional argument
> with the e-mail address or maybe just a domain. Or maybe it is
> acceptable to just supply an address override to message_originator()
> before calling fetch_author_policy()

(requested by Mark Martinec)

[Mark Martinec]

This is apparently already implemented since 0.31,
but not documented in fetch_author_policy.