this gets rid of a warning about signed/unsigned comparison

This is a backport of 0a5338e0 that
accidentally only went into master

Clock skew made this situation way too frequent so we demoted it to
"protocol_warn", but when there's an authority, it should really just
be warn.

This is a backport of bed79c47 which
accidentally only went into master

In particular:
* Disallow "0x10::"
* Don't blow up on ":"
* Disallow "::10000"

Completely disable stats if we aren't running as a relay. We won't
collect any anyway, so setting up the infrastructure for them and
logging about them is wrong. This also removes a confusing log
message that clients without a geoip db would have seen.

Fixes bug 4353.

somebody should s/authoritative directory server/directory authority/g
at some point

If we haven't set real_addr on a connection, we also now that _base.addr
hasn't been tampered with. So we can use that.

Reported by "troll_un"; bugfix on 0.2.0.10-alpha; fixes bug 4349.

This is a fancier bug4457 workaround for 0.2.3.  In 0.2.2, we could
just tell Libevent "Don't enable locking!" so it wouldn't try to make
the event_base notifiable.  But for IOCP, we need a notifiable base.
(Eventually, we'll want a notifiable base for other stuff, like
multithreaded crypto.)  So the solution is to try a full-featured
initialization, and then retry with all the options turned off if that
fails.

Conflicts:
	src/common/compat_libevent.c

Resolving conflict by not taking 7363eae1 ("Use the
EVENT_BASE_FLAG_NOLOCK flag to prevent socketpair() invocation"): in
Tor 0.2.3.x, we _do_ sometimes use notifiable event bases.

In Tor 0.2.2, we never need the event base to be notifiable, since we
don't call it from other threads.  This is a workaround for bug 4457,
which is not actually a Tor bug IMO.