o Major features
   - Tor can now optionally build with the "bufferevents" buffered IO
     backend provided by Libevent, when building with Libevent 2.0.7-rc
     or later.  To use this feature, make sure you have the latest possible
     version of Libevent, and run autoconf with the --enable-bufferevents
     flag.  Using this feature will make our networking code more flexible,
     lets us stack layers on each other, and let us use more efficient
     zero-copy transports where available.