Allow relays to have an IPv6 DirPort on the same port as the IPv4 DirPort
Currently, to do this, relay operators need to say DirPort [IPv6-address]:80 NoAdvertise, or they get a warning "Can't advertise more than one DirPort."
This supports clients on IPv6 in 0.2.8.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information