Address torrc option is ignored if set second time for the IPv6 address

Currently if we specify Address 2 times in the same torrc, once for IPv4 address and once for IPv6 address, it will just ignore the second entry as like it would be for the same IP family:

[warn] Option 'Address' used more than once; all but the last value will be ignored.

This behavior is perfect for cases where operators specify more addresses from the same family (like IPv4 for example) in the same torrc. I am marking this Low priority because it's here only to remind us about it when IPv6 autodetection will be implemented.

I know currently does not do IPv6 address detection so I am guessing this is why it currently does not care to learn about an IPv6 address from Address torrc setting, and only from ORPort to build just descriptors and be optimistic about getting the ReachableIPv6 flag, but when this changes it should be possible to specify Address 2 times in torrc, once for IPv4 and once for IPv6, the same as for OutboundBindAddress | OutboundBindAddressOR | OutboundBindAddressExit.