tor/changes/bufferevent-support

 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.
   - As an experimental feature, when using the "bufferevents" buffered
     IO backend, Tor can try to use Windows's IOCP networking API.  This
     is off by default.  To turn it on, add "DisableIOCP 0" to your torrc.