Warn if Tor is a relay and a HS

Closes 12908; see #8742
Correctly update channel local mark when address of incoming connection changes after handshake; fixes bug #12160
Merge remote-tracking branch 'andrea/bug12160_025' into maint-0.2.5
Merge remote-tracking branch 'public/bug12908_025' into maint-0.2.5
In routerlist_assert_ok(), check r2 before taking &(r2->cache_info)

Technically, we're not allowed to take the address of a member can't
exist relative to the null pointer.  That makes me wonder how any sane
compliant system implements the offsetof macro, but let's let sleeping
balrogs lie.

Fixes 13096; patch on 0.1.1.9-alpha; patch from "teor", who was using
clang -fsanitize=undefined-trap -fsanitize-undefined-trap-on-error -ftrapv
Reduce log severity for unused ClientTransportPlugin lines

Tor Browser includes several ClientTransportPlugin lines in its
torrc-defaults file, leading every Tor Browser user who looks at her
logs to see these notices and wonder if they're dangerous.

Resolves bug 13124; bugfix on 0.2.5.3-alpha.
Merge remote-tracking branch 'origin/maint-0.2.5' into release-0.2.5
Fold changes entries into 0.2.5.7 changelog