o Minor bugfixes
   - Alter circuit build timeout measurement to start at the point
     where we begin the CREATE/CREATE_FAST step (as opposed to circuit
     initialization). This should make our timeout measurements more
     uniform. Previously, we were sometimes including ORconn setup time
     in our circuit build time measurements. Fixes bug #3443.

 o Minor features
   - If we have no circuits open, use a relaxed timeout (the 95-percentile
     cutoff) until a circuit succeeds. This should allow Tor to succeed
     building circuits if the network connection drastically changes.