rfc2104.el was rewritten for speed in 2008, and seems to be about
twice as fast as hmac-*.el.  I think hmac-*.el could be deprecated and
eventually removed; the only use in the Emacs tree is in sasl-cram.el.

So here is a new and improved patch for implementing SCRAM-SHA-1, that
uses the existing rfc2104.el instead of adding hmac-sha1.el.

Would it be okay for a module in lisp/net to depend on a module in
lisp/gnus?

Regards,
Magnus