merge #10968: commit threading doc changes and corresponding whatsnew entry.

It is unfortunate that the '_' names were not kept as aliases, and that RLock
was not also converted to a class, but it is now too late to change either of
those things for 3.3.
diff --git a/Misc/HISTORY b/Misc/HISTORY
index c5149be..728402e 100644
--- a/Misc/HISTORY
+++ b/Misc/HISTORY
@@ -2907,11 +2907,11 @@
 - Issue #8887: "pydoc somebuiltin.somemethod" (or help('somebuiltin.somemethod')
   in Python code) now finds the doc of the method.
 
-- Issue #10968: Remove indirection in threading.  The public names (Thread,
+- Issue #10968: Remove indirection in threading.  The public names (Event,
   Condition, etc.) used to be factory functions returning instances of hidden
-  classes (_Thread, _Condition, etc.), because (if Guido recalls correctly) this
-  code pre-dates the ability to subclass extension types.  It is now possible to
-  inherit from Thread and other classes, without having to import the private
+  classes (_Event, _Condition, etc.), because (if Guido recalls correctly) this
+  code pre-dates the ability to subclass extension types.  It is now possible
+  to inherit from these classes without having to import the private
   underscored names like multiprocessing did.
 
 - Issue #9723: Add shlex.quote functions, to escape filenames and command