Merge fixes for #12256 and typos from 3.2

Doc/distutils/install.rst

@@ -101,7 +101,7 @@ one command from a terminal::
 
    python setup.py install
 
-For Windows, this command should be run from a command prompt windows
+For Windows, this command should be run from a command prompt window
 (:menuselection:`Start --> Accessories`)::
 
    setup.py install

Doc/distutils/setupscript.rst

@@ -254,7 +254,7 @@ code: it's probably better to write C code like  ::
 
 If you need to include header files from some other Python extension, you can
 take advantage of the fact that header files are installed in a consistent way
-by the Distutils :command:`install_header` command.  For example, the Numerical
+by the Distutils :command:`install_headers` command.  For example, the Numerical
 Python header files are installed (on a standard Unix installation) to
 :file:`/usr/local/include/python1.5/Numerical`. (The exact location will differ
 according to your platform and Python installation.)  Since the Python include

Doc/glossary.rst

@@ -30,7 +30,10 @@ Glossary
       Abstract base classes complement :term:`duck-typing` by
       providing a way to define interfaces when other techniques like
       :func:`hasattr` would be clumsy or subtly wrong (for example with
-      :ref:`magic methods <special-lookup>`). Python comes with many built-in ABCs for
+      :ref:`magic methods <special-lookup>`).  ABCs introduce virtual
+      subclasses, which are classes that don't inherit from a class but are
+      still recognized by :func:`isinstance` and :func:`issubclass`; see the
+      :mod:`abc` module documentation.  Python comes with many built-in ABCs for
       data structures (in the :mod:`collections.abc` module), numbers (in the
       :mod:`numbers` module), streams (in the :mod:`io` module), import finders
       and loaders (in the :mod:`importlib.abc` module).  You can create your own