Login fails on fcgid-based PHP setups

Regarding the following code:

function shibboleth_session_active()
{
	return apply_filters('shibboleth_session_active', isset($_SERVER['Shib-Session-ID']));
}

This fails on our fcgid-based PHP infrastructure. What we have found is that the name is changed at some point between mod_shib and WordPress and so it requires $_SERVER['Shib_Session_ID'] instead.

This breaks standard mod_php setups, though, so I believe shibboleth_session_active() will need to be aware of both and grab whichever one happens to be populated.