* smtp.el: Bind `sasl-mechanisms'; add autoload settings for

* smtp.el: Bind `sasl-mechanisms'; add autoload settings for
`sasl-make-principal', `sasl-find-authenticator',
`sasl-authenticator-mechanism-internal' and
`sasl-evaluate-challenge'.
(smtp-use-sasl): New user option.
(smtp-sasl-principal-name): New user option.
(smtp-sasl-mechanisms): New user option.
(smtp-submit-package): Call `smtp-primitive-starttls' and
`smtp-primitive-auth'.
(smtp-primitive-ehlo): Don't modify the rest of a extension line.
(smtp-primitive-auth): New function.
(smtp-primitive-starttls): Check the response code.

* sasl.el: New implementation.

* sasl-cram.el: New file.

* FLIM-ELS (flim-modules): Add `md5', `md5-el', `md5-dl',
`hex-util', `hmac-def', `hmac-md5', `sasl' and `sasl-cram'.