XML parsing should be more strict

[Aaron1011]

quick_xml seems to accept XML like <>, which Flash's XML parser rejects. Some SWFs (like Scratch) do new XML(maybe_xml_data) and catch thrown error to detect invalid XML, so we need to match Flash's parsing behavior.

[Lord-McSweeney]

AFAIK this is the opposite for AVM1, where XML parsing needs to be less strict.

[Aaron1011]

Opened tafia/quick-xml#622 upstream for one particular case of invalid XML being accepted.

[evilpie]

So that case should be fixed now, but I guess there are still other differences.