tor/changes/threads-required

  o Removed features:
    - Tor no longer supports systems without threading support.
      When we began working on Tor, there were several systems that didn't
      have threads, or where the thread support wasn't able to run the
      threads of a single process on multiple CPUs. That no longer holds:
      every system where Tor needs to run well now has threading support.
      Resolves ticket 12439.

  o Minor features:
    - Threads are no longer disabled by default on Solaris; we believe that
      the versions of Solaris with broken threading support are all obsolete
      by now. Resolves ticket 9495.