Issue #12196: Add a note on os.pipe2() in the "Whats' new in Python 3.3"

document.

Doc/whatsnew/3.3.rst

@@ -106,6 +106,11 @@ connection when done::
 os
 --
 
+* The :mod:`os` module has a new :func:`~os.pipe2` function that makes it
+  possible to create a pipe with :data:`~os.O_CLOEXEC` or
+  :data:`~os.O_NONBLOCK` flags set atomically. This is especially useful to
+  avoid race conditions in multi-threaded programs.
+
 * The :mod:`os` module has a new :func:`~os.sendfile` function which provides
   an efficent "zero-copy" way for copying data from one file (or socket)
   descriptor to another. The phrase "zero-copy" refers to the fact that all of