o Major bugfixes:
    - When weighting bridges, we used to trust the bandwidths they provided
      in their descriptor, only capping them at 10MB/s. This turned out to be
      problematic for two reasons: Bridges could claim to handle a lot more
      traffic then they actually would, thus making more clients pick them and
      have a pretty effective DoS attack. The other issue is that new bridges
      that might not have a good estimate for their bw capacity yet would not
      get used at all unless no other bridges are available to a client.
      This fixes bug 1912; bugfix on 0.2.2.7-alpha.