#652749: document the constants added to the builtins by site.py.

Doc/library/constants.rst

-
 Built-in Constants
 ==================
 
@@ -47,4 +46,28 @@ A small number of constants live in the built-in namespace.  They are:
 
    This constant is true if Python was not started with an :option:`-O` option.
    Assignments to :const:`__debug__` are illegal and raise a :exc:`SyntaxError`.
-   See also the :keyword:`assert` statement.
\ No newline at end of file
+   See also the :keyword:`assert` statement.
+
+
+Constants added by the :mod:`site` module
+-----------------------------------------
+
+The :mod:`site` module (which is imported automatically during startup, except
+if the :option:`-S` command-line option is given) adds several constants to the
+built-in namespace.  They are useful for the interactive interpreter shell and
+should not be used in programs.
+
+.. data:: quit([code=None])
+          exit([code=None])
+
+   Objects that when printed, print a message like "Use quit() or Ctrl-D
+   (i.e. EOF) to exit", and when called, raise :exc:`SystemExit` with the
+   specified exit code, and when .
+
+.. data:: copyright
+          license
+          credits
+
+   Objects that when printed, print a message like "Type license() to see the
+   full license text", and when called, display the corresponding text in a
+   pager-like fashion (one screen at a time).

Doc/library/functions.rst

@@ -511,6 +511,8 @@ available.  They are listed here in alphabetical order.
    topic, and a help page is printed on the console.  If the argument is any other
    kind of object, a help page on the object is generated.
 
+   This function is added to the built-in namespace by the :mod:`site` module.
+
    .. versionadded:: 2.2