Merge from 3.3

diff --cc Doc/glossary.rst
index 2f658aca097197ff36e2d63960a2b3b4202323bb,b48eb1ed5f76129a8cb204d16df9e8e8a1705713..f71a1f72e5731996f5a50a4d65dd3d19f1630f51
--- 1/Doc/glossary.rst
--- 2/Doc/glossary.rst
+++ b/Doc/glossary.rst
@@@ -783,10 -763,14 +783,18 @@@ Glossar
        mapping rather than a sequence because the lookups use arbitrary
        :term:`immutable` keys rather than integers.
  
+       The :class:`collections.abc.Sequence` abstract base class
+       defines a much richer interface that goes beyond just
+       :meth:`__getitem__` and :meth:`__len__`, adding :meth:`count`,
+       :meth:`index`, :meth:`__contains__`, and
+       :meth:`__reversed__`. Types that implement this expanded
+       interface can be registered explicitly using
+       :func:`~abc.register`.
+ 
 +   single dispatch
 +      A form of :term:`generic function` dispatch where the implementation is
 +      chosen based on the type of a single argument.
 +
     slice
        An object usually containing a portion of a :term:`sequence`.  A slice is
        created using the subscript notation, ``[]`` with colons between numbers

diff --cc Doc/library/ipaddress.rst
Simple merge