Compatibility problem with lighttpd due to 'Expect: 100-continue" header

In some configurations Moodle Networking will break on lighttpd servers. This is due to a bug in lighttpd, which does not correctly handle 'Expect' headers. The server will return a 417 error (note that mnet could probably use a bit more error checking), failing to return the public key from the remote site.

The fix seems to be to suppress the header, thus...

curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: text/xml charset=UTF-8","Expect:"));

...in the list of options in the mnet_get_public_key function in mnet/lib.php.

I really need to test this more extensively on non-lighttpd servers, but so far it doesn't seem to break anything. If it's ok, I'd like to just include it so that it works properly for lighttpd.