tor/changes/feature5956

  o Major features:
    - When deciding whether we have enough descriptors to build circuits,
      instead of looking at raw circuit counts, look at which fraction of
      (bandwidth-weighted) paths we're able to build. This approach keeps
      clients from building circuits if their paths are likely to stand out
      statistically. The default fraction of paths needed is taken from the
      consensus directory; you can override it with the new
      PathsNeededToBuildCircuits option.  Fixes issue 5956.