This is a kludge to deal with the fact that `tor_addr_t` doesn't contain
`sun_path`.  This currently ONLY happens when circuit isolation is being
checked, for an isolation mode that is force disabled anyway, so the
kludge is "ugly but adequate", but realistically, making `tor_addr_t`
and the AF_UNIX SocksPort code do the right thing is probably the better
option.

The client addr is essentially meaningless in this context (yes, it is
possible to explicitly `bind()` AF_LOCAL client side sockets to a path,
but no one does it, and there are better ways to grant that sort of
feature if people want it like using `SO_PASSCRED`).

As a failsafe, we should make sure that no authority ever votes for
a set of protocol versions that it does not itself support.

As before, we check server protocols whenever server_mode(options)
is true and we check client protocols whenever server_mode(options)
is false.

Additionally, we now _also_ check client protocols whenever any
client port is set.

(Technically, we could just remove extend2 cell checking entirely,
since all Tor versions on our network are required to have it, but
let's keep this around as an example of How To Do It.)

(Despite the increased size of the consensus, this should have
approximately zero effect on the compressed consensus size, since
the "proto" line should be completely implied by the "v" line.)

Also, detect an additional failure type. Thanks, tests!

(How distinctly I recall thee)

[This is a brute-force method that potentially uses way too much
RAM. Need to rethink this a little. Right now you can DOS an
authority by saying "Foo=1-4294967295".]

Sierra provides clock_gettime(), but not pthread_condattr_setclock.
So we had better lot try to use CLOCK_MONOTONIC as our source for
time when waiting, since we ccan never actually tell the condition
that we mean CLOCK_MONOTONIC.

This isn't a tor bug yet, since we never actually pass a timeout to
tor_cond_wait() outside of the unit tests.