Assigning a second IPv6 with rtsol

[Niklaas Baudet von Gersdorff]

I successfully managed to enable IPv6 on my RPi2 with 11-CURRENT by
adding the following lines to /etc/rc.conf

```
ifconfig_ue0_ipv6="inet6 accept_rtadv"
rtsold_enable="YES"

```

executing

```
ifconfig ue0 inet6 -ifdisabled

```

and running `rtsol`. Next to the IPv4 address that got assigned through
DHCP I also have an IPv6 address assigned by my local router. Everything
works as expected.

In the next step I would like to assign a second IPv6 that I do not
specify manually but that gets, as the first one, assigned by my local
router. Is that possible?

I know how to assign an additional address with `ifconfig ... alias` but
only how to do so with manually specified addresses. What I actually
want to achieve is that I get another IPv6 by my local router/ISP
automatically to eventually attach it to a jail.

-- 
Niklaas