I believe the newlogin feature was just introduced in xscreensaver-5.00 which came out just recently. Be sure to enable the new-login USE flag in /etc/portage/package.use for x11-misc/xscreensaver.
I've tried xscreensaver-4.24 and 5.00 both compiled with new-login and I don't see any kind of a new login button on the locked screen display. How can I get that to work? - Grant -- gentoo-user@gentoo.org mailing list