bpo-33832: Add "magic method" glossary entry (GH-7630)

Doc/glossary.rst

@@ -663,6 +663,11 @@ Glossary
       :term:`finder`. See :pep:`302` for details and
       :class:`importlib.abc.Loader` for an :term:`abstract base class`.
 
+   magic method
+      .. index:: pair: magic; method
+
+      An informal synonym for :term:`special method`.
+
    mapping
       A container object that supports arbitrary key lookups and implements the
       methods specified in the :class:`~collections.abc.Mapping` or
@@ -1004,6 +1009,8 @@ Glossary
       (subscript) notation uses :class:`slice` objects internally.
 
    special method
+      .. index:: pair: special; method
+
       A method that is called implicitly by Python to execute a certain
       operation on a type, such as addition.  Such methods have names starting
       and ending with double underscores.  Special methods are documented in

Misc/NEWS.d/next/Documentation/2018-06-15-15-57-37.bpo-33832.xBFhKw.rst

+Add glossary entry for 'magic method'.