[exim] Exim, TLS, and SSL cert passwords.

At http://www.gnode.net/basic-exim-config-with-plain-auth-over-tls/, the
Exim configuration file says in the comments that the private key must
*not* have a password.

Unfortunately, our certificate issuer requires it now.

So what do I do to get Exim to use the certificate password? This works
fine in Dovecot.