Report XML::Twig version when testing entities (GH#7)

GH#7 is related to the old XML::Twig bug RT#86633

In my tests, this crash doesn't happen with latest XML::Twig version (but other problems could pop up, like disappearing ampersand RT#93604) or with my patched XML::Twig 3.44 https://github.com/melmothx/xmltwig/tree/topic/fix-escaping

Upstream says the current #93604 bug will be fixed soon. RT#86633 was superseded by latest release.