Weakening of signatures while crying.

This works around a bizzare error from Method::Signatures claiming
that Exobrain::run() expects zero arguments, when really it's being
called correctly. It only manifests with Action::SendmailXP.

I suspect that BUILD() in Agent::Depends was being passed args,
we were denying their existence, and Method::Signatures was somehow
coming up with a bogus error location.