updates to Digest test site

<http://portal.research.bell-labs.com:8000>

I've changed the behavior of my Digest server test site to reflect the
Rev05 HTTP/1.1 specification.  In particular,

1) The server will prompt with qop="auth,auth-int" only when the request
is HTTP/1.1 *and* it sees a TE: trailers header.  (The server *always*
sends the auth-int Authentication-Info in a trailer.)

2) The server will send Trailer: Authentication-Info when it sends
Authentication-Info in a trailer.

Dave Kristol