- update to 3.2.1:
* The methods ``apply_templates()`` and ``process_children()`` of XSLT
extension elements have gained two new boolean options ``elements_only``
and ``remove_blank_text`` that discard either all strings or whitespace-only
strings from the result list.
* When moving Elements to another tree, the namespace cleanup mechanism
no longer drops namespace prefixes from attributes for which it finds
a default namespace declaration, to prevent them from appearing as
unnamespaced attributes after serialisation.
* Returning non-type objects from a custom class lookup method could lead
to a crash.
* Instantiating and using subtypes of Comments and ProcessingInstructions
crashed.