I wanted mpd to play a mp3 stream from a music website.  The stream is
only available to subscribers, which restriction is enforced through
normal http authentication.  However, the URL I get from the website
is not the final URL of the stream, but a generic URL which points to
the real one through a redirect (code 301).  Thus, I cannot predict
the final URL, and so I cannot use the username:password hack to force
the authentication, and mpd (libcurl on mpds behalf) fails to grab the
stream.

libcurl allows the option CURLOPT_NETRC to be set and then the
credentials can be stored in the good old .netrc file (in this case it
would be ~mpd/.netrc, of course).  But mpd doesn't set this option.  I
think it should.