o Minor bugfixes (compilation):
    - Avoid using labs() on time_t, which can cause compilation warnings
      on 64-bit Windows builds.  Fixes bug 31343; bugfix on 0.2.4.4-alpha.

  o Minor bugfixes (clock skew detection):
    - Don't believe clock skew results from NETINFO cells that appear to
      arrive before the VERSIONS cells they are responding to were sent.
      Previously, we would accept them up to 3 minutes "in the past".
      Fixes bug 31343; bugfix on 0.2.4.4-alpha.