Synchronize glossary with py3k.

This update includes new entries that apply to 2.7 too, mention of class
decorators, mention of nonlocal, notes about bytecode, markup fixes and
some rewrappings.  Future backports of changes should be slightly
easier.

Doc/glossary.rst

@@ -58,11 +58,14 @@ Glossary
 
    bytecode
       Python source code is compiled into bytecode, the internal representation
-      of a Python program in the interpreter.  The bytecode is also cached in
-      ``.pyc`` and ``.pyo`` files so that executing the same file is faster the
-      second time (recompilation from source to bytecode can be avoided).  This
-      "intermediate language" is said to run on a :term:`virtual machine`
-      that executes the machine code corresponding to each bytecode.
+      of a Python program in the CPython interpreter.  The bytecode is also
+      cached in ``.pyc`` and ``.pyo`` files so that executing the same file is
+      faster the second time (recompilation from source to bytecode can be
+      avoided).  This "intermediate language" is said to run on a
+      :term:`virtual machine` that executes the machine code corresponding to
+      each bytecode. Do note that bytecodes are not expected to work between
+      different Python virtual machines, nor to be stable between Python
+      releases.
 
       A list of bytecode instructions can be found in the documentation for
       :ref:`the dis module <bytecodes>`.
@@ -128,8 +131,9 @@ Glossary
          def f(...):
              ...
 
-      See :ref:`the documentation for function definition <function>` for more
-      about decorators.
+      The same concept exists for classes, but is less commonly used there.  See
+      the documentation for :ref:`function definitions <function>` and
+      :ref:`class definitions <class>` for more about decorators.
 
    descriptor
       Any *new-style* object which defines the methods :meth:`__get__`,
@@ -165,8 +169,8 @@ Glossary
       well-designed code improves its flexibility by allowing polymorphic
       substitution.  Duck-typing avoids tests using :func:`type` or
       :func:`isinstance`.  (Note, however, that duck-typing can be complemented
-      with :term:`abstract base class`\ es.)  Instead, it typically employs
-      :func:`hasattr` tests or :term:`EAFP` programming.
+      with :term:`abstract base classes <abstract base class>`.)  Instead, it
+      typically employs :func:`hasattr` tests or :term:`EAFP` programming.
 
    EAFP
       Easier to ask for forgiveness than permission.  This common Python coding
@@ -178,17 +182,34 @@ Glossary
 
    expression
       A piece of syntax which can be evaluated to some value.  In other words,
-      an expression is an accumulation of expression elements like literals, names,
-      attribute access, operators or function calls which all return a value.
-      In contrast to many other languages, not all language constructs are expressions.
-      There are also :term:`statement`\s which cannot be used as expressions,
-      such as :keyword:`print` or :keyword:`if`.  Assignments are also statements,
-      not expressions.
+      an expression is an accumulation of expression elements like literals,
+      names, attribute access, operators or function calls which all return a
+      value.  In contrast to many other languages, not all language constructs
+      are expressions.  There are also :term:`statement`\s which cannot be used
+      as expressions, such as :keyword:`print` or :keyword:`if`.  Assignments
+      are also statements, not expressions.
 
    extension module
       A module written in C or C++, using Python's C API to interact with the
       core and with user code.
 
+   file object
+      An object exposing a file-oriented API (with methods such as
+      :meth:`read()` or :meth:`write()`) to an underlying resource.  Depending
+      on the way it was created, a file object can mediate access to a real
+      on-disk file or to another other type of storage or communication device
+      (for example standard input/output, in-memory buffers, sockets, pipes,
+      etc.).  File objects are also called :dfn:`file-like objects` or
+      :dfn:`streams`.
+
+      There are actually three categories of file objects: raw binary files,
+      buffered binary files and text files.  Their interfaces are defined in the
+      :mod:`io` module.  The canonical way to create a file object is by using
+      the :func:`open` function.
+
+   file-like object
+      A synonym for :term:`file object`.
+
    finder
       An object that tries to find the :term:`loader` for a module. It must
       implement a method named :meth:`find_module`. See :pep:`302` for
@@ -335,7 +356,7 @@ Glossary
       slowly.  See also :term:`interactive`.
 
    iterable
-      A container object capable of returning its members one at a
+      An object capable of returning its members one at a
       time. Examples of iterables include all sequence types (such as
       :class:`list`, :class:`str`, and :class:`tuple`) and some non-sequence
       types like :class:`dict` and :class:`file` and objects of any classes you
@@ -404,6 +425,12 @@ Glossary
       the :term:`EAFP` approach and is characterized by the presence of many
       :keyword:`if` statements.
 
+      In a multi-threaded environment, the LBYL approach can risk introducing a
+      race condition between "the looking" and "the leaping".  For example, the
+      code, ``if key in mapping: return mapping[key]`` can fail if another
+      thread removes *key* from *mapping* after the test, but before the lookup.
+      This issue can be solved with locks or by using the EAFP approach.
+
    list
       A built-in Python :term:`sequence`.  Despite its name it is more akin
       to an array in other languages than to a linked list since access to
@@ -424,7 +451,8 @@ Glossary
 
    mapping
       A container object that supports arbitrary key lookups and implements the
-      methods specified in the :class:`Mapping` or :class:`MutableMapping`
+      methods specified in the :class:`~collections.Mapping` or
+      :class:`~collections.MutableMapping`
       :ref:`abstract base classes <collections-abstract-base-classes>`.  Examples
       include :class:`dict`, :class:`collections.defaultdict`,
       :class:`collections.OrderedDict` and :class:`collections.Counter`.
@@ -448,6 +476,14 @@ Glossary
       its first :term:`argument` (which is usually called ``self``).
       See :term:`function` and :term:`nested scope`.
 
+   method resolution order
+      Method Resolution Order is the order in which base classes are searched
+      for a member during lookup. See `The Python 2.3 Method Resolution Order
+      <http://www.python.org/download/releases/2.3/mro/>`_.
+
+   MRO
+      See :term:`method resolution order`.
+
    mutable
       Mutable objects can change their value but keep their :func:`id`.  See
       also :term:`immutable`.
@@ -480,10 +516,11 @@ Glossary
    nested scope
       The ability to refer to a variable in an enclosing definition.  For
       instance, a function defined inside another function can refer to
-      variables in the outer function.  Note that nested scopes work only for
-      reference and not for assignment which will always write to the innermost
-      scope.  In contrast, local variables both read and write in the innermost
-      scope.  Likewise, global variables read and write to the global namespace.
+      variables in the outer function.  Note that nested scopes by default work
+      only for reference and not for assignment.  Local variables both read and
+      write in the innermost scope.  Likewise, global variables read and write
+      to the global namespace.  The :keyword:`nonlocal` allows writing to outer
+      scopes.
 
    new-style class
       Any class which inherits from :class:`object`.  This includes all built-in
@@ -506,9 +543,9 @@ Glossary
       :term:`argument`.
 
    Python 3000
-      Nickname for the next major Python version, 3.0 (coined long ago
-      when the release of version 3 was something in the distant future.)  This
-      is also abbreviated "Py3k".
+      Nickname for the Python 3.x release line (coined long ago when the release
+      of version 3 was something in the distant future.)  This is also
+      abbreviated "Py3k".
 
    Pythonic
       An idea or piece of code which closely follows the most common idioms
@@ -531,7 +568,7 @@ Glossary
       object drops to zero, it is deallocated.  Reference counting is
       generally not visible to Python code, but it is a key element of the
       :term:`CPython` implementation.  The :mod:`sys` module defines a
-      :func:`getrefcount` function that programmers can call to return the
+      :func:`~sys.getrefcount` function that programmers can call to return the
       reference count for a particular object.
 
    __slots__
@@ -567,7 +604,15 @@ Glossary
    statement
       A statement is part of a suite (a "block" of code).  A statement is either
       an :term:`expression` or a one of several constructs with a keyword, such
-      as :keyword:`if`, :keyword:`while` or :keyword:`print`.
+      as :keyword:`if`, :keyword:`while` or :keyword:`for`.
+
+   struct sequence
+      A tuple with named elements. Struct sequences expose an interface similiar
+      to :term:`named tuple` in that elements can either be accessed either by
+      index or as an attribute. However, they do not have any of the named tuple
+      methods like :meth:`~collections.somenamedtuple._make` or
+      :meth:`~collections.somenamedtuple._asdict`. Examples of struct sequences
+      include :data:`sys.float_info` and the return value of :func:`os.stat`.
 
    triple-quoted string
       A string which is bound by three instances of either a quotation mark