move libevent into base

third_party/libevent/whatsnew-14.txt

-What's New In Libevent 1.4:
-
-0. About this document
-
-  This document describes the key differences between Libevent 1.3 and
-  Libevent 1.4, from a user's point of view.  It was most recently
-  updated based on features from libevent 1.4.2-rc.
-
-1. Packaging Issues.
-
-1.1. The great library division.
-
-  The libevent source now builds two libraries: libevent_core and
-  libevent_extra.  The libevent_core library includes event loops,
-  timers, buffer code, and various small compatibility functions.  The
-  libevent_extra library includes code for HTTP, DNS, RPC, and so on.
-  Thus, if you're writing software that only uses libevent's event
-  loop, you should link against only the libevent_core library,
-  whereas if you're writing software that uses libevent's protocol
-  support as well, you need to link libevent_extra as well.
-
-  For backward compatibility, libevent also builds a library called
-  "libevent" that includes everything.
-
-1.2. The event-config.h header
-
-  Libevent configure script now builds two headers from its configure
-  script: config.h (which it uses internally) and event-config.h
-  (which it installs as a header file).  All of the macros in
-  event-config.h are modified so that they're safe to include in other
-  projects.  This allows libevent's header files (like event.h and
-  evutil.h) information about platform configuration.
-
-  What does this mean for you?  As of 1.4.x, it should never be
-  necessary to include extra files or define extra types before you
-  include event.h (or any other libevent header); event.h can now look
-  at the information in event-config.h and figure out what it needs to
-  include.
-
-1.3. Documentation
-
-  Libevent now includes better doxygen documentation.  It's not
-  perfect or complete, though; if you find a mistake, please let us
-  know.
-
-1.4. Libtool usage
-
-  We now use libtool's library versioning support correctly.  If we
-  don't mess this up, it means that binaries linked against old
-  version of libevent should continue working when we make changes to
-  libevent that don't break backward compatibility.
-
-1.5. Portability
-
-  Libevent now builds with MSVC again.  We've only tested it with MSVC
-  2005, and the project files might not be right.  Please let us know
-  if you run into any issues.
-
-  Libevent now builds on platforms where /bin/sh is not bash.
-
-  Libevent's regression test no longer requires Python to be
-  installed.
-
-2. New and Improved APIs:
-
-  (This list includes functions that are new, functions whose behavior
-  has changed, and functions that were included in previous releases
-  but which never actually worked before.)
-
-2.1. Utility functions are defined in evutil.h
-
-  Libevent now exposes a small set of functions for cross-platform
-  network programming in evutil.h, on the theory that they've been
-  useful enough to us that other people may likely want to use them
-  too.  These are mainly workarounds for Windows issues for now: they
-  include evutil_socketpair (to fake socketpair on platforms that
-  don't have it) and evutil_make_socket_nonblocking (to make a socket
-  nonblocking in a cross-platform way.  See the header for more
-  information.
-
-2.2. In the libevent core.
-
-  The event_base_free() function now works.  Previously, it would
-  crash with an assertion failure if there were events pending on a
-  base.  Now, it simply deletes all the pending events and frees the
-  base.  Be careful -- this might leak fds and memory associated with
-  the old events.  To avoid leaks, you should still remove all the
-  events and free their resources before you delete the base.
-
-  Libevent should now work properly with fork().  Just call
-  event_reinit() on your event base after the fork call, and it should
-  work okay.  Please let us know about any bugs you find.
-
-  There's a new event_base_new() function that acts just like
-  event_init(), but does not replace the default base.  If you are
-  using multiple event bases in your code, you should just use
-  event_base_new() instead of event_init(), to avoid accidental bugs.
-
-  There's new event_loopbreak() function to make a current event loop
-  stop exiting and return.  Unlike event_loopexit, it stops subsequent
-  pending events from getting executed.  This behavior is useful for
-  scripting languages to implement exceptions from inside callbacks.
-
-  There's a new event_base_get_method() function, for use in place of
-  event_get_method() in multi-base applications.
-
-2.3. New in HTTP.
-
-  There's an evhttp_connection_set_local_address() function you can
-  use to set the local address of an HTTP connection.
-
-  HTTP/1.1 chunking now correctly ends chunks with '\r\n'.
-
-2.4. New in DNS
-
-  Instead of picking your method for generating DNS transaction IDs at
-  startup, you can use evdns_set_transaction_id() to provide a
-  transaction ID function at runtime.
-
-  The "class" field in evdns_server_request is now renamed to
-  dns_question_class, so that it won't break compilation under C++.
-  This uses some preprocessor hacks so that C code using the old name
-  won't break.  Eventually, the old name will be deprecated entirely;
-  please don't use it.
-
-2.5. New in RPC
-
-  There are now hooks on RPC input and output; can be used to
-  implement RPC independent processing such as compression or
-  authentication.
-
-  RPC tags can now be up to 32 bits.  This is wire-compatible, but
-  changes some of the types in the APIs.  Please let us know if this
-  is problematic for you.
-
-3. Big bugfixes
-
-  We've done a lot, with help from users on different platforms, to
-  make the different backends behave more similarly with respect to
-  signals and timeouts.  The kqueue and solaris backends were the big
-  offenders previously, but they should be better now.  Windows should
-  be better too, though it's likely that problems remain there.
-
-  The libevent headers (though not the source files!) should now build
-  cleanly on C++.
-
-  (For more bugfixes, see the ChangeLog file.  These are only the
-  biggies.)
-
-4. Big performance improvements
-
-  Libevent now uses a min-heap rather than a red-black tree to track
-  timeouts.  This means that finding the next timeout to fire is now
-  O(1) instead of (lg n).
-
-  The win32 select-based backend now uses a red-black tree to map
-  SOCKET handles to event structures.  This changes the performance
-  characteristics of the event loop on win32 from O(n^2) to O(n lg n).
-  Not perfect, but better.
-
-5. Removed code and features
-
-  The rtsig backend is now removed.  It hasn't even compiled for a
-  while, and nobody seemed to miss it very much.  All the platforms
-  that have rtsig seem to have a better option instead these days.
-  Please let us know if rtsig was crucial for you.
-