#15543: glossary entry for and 'universal newlines', and links to it.

Patch by Chris Jerdonek.
diff --git a/Doc/library/zipfile.rst b/Doc/library/zipfile.rst
index bcec134..4035a14 100644
--- a/Doc/library/zipfile.rst
+++ b/Doc/library/zipfile.rst
@@ -169,13 +169,17 @@
    Return a list of archive members by name.
 
 
+.. index::
+   single: universal newlines; zipfile.ZipFile.open method
+
 .. method:: ZipFile.open(name, mode='r', pwd=None)
 
    Extract a member from the archive as a file-like object (ZipExtFile). *name* is
    the name of the file in the archive, or a :class:`ZipInfo` object. The *mode*
    parameter, if included, must be one of the following: ``'r'`` (the  default),
-   ``'U'``, or ``'rU'``. Choosing ``'U'`` or  ``'rU'`` will enable universal newline
-   support in the read-only object. *pwd* is the password used for encrypted files.
+   ``'U'``, or ``'rU'``. Choosing ``'U'`` or  ``'rU'`` will enable
+   :term:`universal newlines` support in the read-only object.
+   *pwd* is the password used for encrypted files.
    Calling  :meth:`open` on a closed ZipFile will raise a  :exc:`RuntimeError`.
 
    .. note::