DirServer lines should take more than one "orport="
In order for clients and relays to be able to contact an authority server over IPv6 we should expand the DirServer line to accept more than one OR port.
Do we prefer "orport=ADDR0,ADDR1,..." or "orport=ADDR0 orport=ADDR1 ..."? Or perhaps something completely different?
Note that an ADDR will be IP-ADDRESS ":" PORT-NUMBER rather than todays PORT-NUMBER..
We need to
- add field(s) to trusted_dir_server_t
- fix the parsing in parse_dir_server_line(), probably by calling tor_addr_port_lookup().
We also need legacy/trac#6772 (moved) (Fall back to alternative OR port if the current fails) to be implemented for this to be useful, f.ex. in directory_post_to_dirservers().