Group the Windows entries in getfilesystemencoding doc, move the win 9x one at...

Group the Windows entries in getfilesystemencoding doc, move the win 9x one at the bottom of the list and fix some markup.

Doc/library/sys.rst

@@ -379,17 +379,19 @@ always available.
    file names, or ``None`` if the system default encoding is used. The result value
    depends on the operating system:
 
-   * On Windows 9x, the encoding is "mbcs".
-
-   * On Mac OS X, the encoding is "utf-8".
+   * On Mac OS X, the encoding is ``'utf-8'``.
 
    * On Unix, the encoding is the user's preference according to the result of
-     nl_langinfo(CODESET), or :const:`None` if the ``nl_langinfo(CODESET)`` failed.
+     nl_langinfo(CODESET), or ``None`` if the ``nl_langinfo(CODESET)``
+     failed.
 
    * On Windows NT+, file names are Unicode natively, so no conversion is
-     performed. :func:`getfilesystemencoding` still returns ``'mbcs'``, as this is
-     the encoding that applications should use when they explicitly want to convert
-     Unicode strings to byte strings that are equivalent when used as file names.
+     performed. :func:`getfilesystemencoding` still returns ``'mbcs'``, as
+     this is the encoding that applications should use when they explicitly
+     want to convert Unicode strings to byte strings that are equivalent when
+     used as file names.
+
+   * On Windows 9x, the encoding is ``'mbcs'``.
 
    .. versionadded:: 2.3