Homogenize the "optional OS services" menu

Doc/library/concurrent.futures.rst

-:mod:`concurrent.futures` --- Concurrent computation
-====================================================
+:mod:`concurrent.futures` --- Launching parallel tasks
+======================================================
 
 .. module:: concurrent.futures
    :synopsis: Execute computations concurrently using threads or processes.

Doc/library/multiprocessing.rst

-:mod:`multiprocessing` --- Process-based "threading" interface
-==============================================================
+:mod:`multiprocessing` --- Process-based parallelism
+====================================================
 
 .. module:: multiprocessing
-   :synopsis: Process-based "threading" interface.
+   :synopsis: Process-based parallelism.
 
 
 Introduction

Doc/library/someos.rst

@@ -14,11 +14,11 @@ some other systems as well (e.g. Windows).  Here's an overview:
 
    select.rst
    threading.rst
-   dummy_threading.rst
-   _thread.rst
-   _dummy_thread.rst
-   concurrent.futures.rst
    multiprocessing.rst
+   concurrent.futures.rst
    mmap.rst
    readline.rst
    rlcompleter.rst
+   dummy_threading.rst
+   _thread.rst
+   _dummy_thread.rst

Doc/library/threading.rst

-:mod:`threading` --- Higher-level threading interface
-=====================================================
+:mod:`threading` --- Thread-based parallelism
+=============================================
 
 .. module:: threading
-   :synopsis: Higher-level threading interface.
+   :synopsis: Thread-based parallelism.
 
 
 This module constructs higher-level threading interfaces on top of the lower