Enhance the docstrings for unicode.split() and string.split()
to make it clear that it is possible to pass None as the
separator argument to get the default "any whitespace" separator.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 05fd11c..722b427 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -5987,8 +5987,8 @@
\n\
Return a list of the words in S, using sep as the\n\
delimiter string. If maxsplit is given, at most maxsplit\n\
-splits are done. If sep is not specified, any whitespace string\n\
-is a separator.");
+splits are done. If sep is not specified or None,
+any whitespace string is a separator.");
static PyObject*
unicode_split(PyUnicodeObject *self, PyObject *args)