Authentication window pops up for logout

I have the securesite only guard some RSS feed paths (so limited to some specific paths, and only seen in RSS readers unless you visit the RSS feeds logged out in a browser). Still, when I log out of the site, an authentication window pops up. I found it is due to securesite_user()'s $op == logout action. Since it is not documented why this requests authentication, I commented out for my own use for now, but there must be a reason (and a better solution).

Throwing up a *login* authentication form on *logout* is quite interesting nonetheless.

BTW patch generated from local SVN repository. Should apply to securesite 5.