Directly store the information contained in $_SERVER['REMOTE_ADDR']
instead of using ip2long() which does not support IPv6 addresses. Note
that the LastLoginIPAddress field is designed to be used by the
administrator on rare occasions only (e.g. to fight spam) and is not
displayed anywhere.

Fixes FS#48557.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>