xml_name_type() should report namespace error if name ends with colon

This means that either there is a non-qualified name colon, or no local name. The WPT tests expect
a NAMESPACE_ERR to be thrown, so this blocks #2185 to some degree

I've re-opened this because I disagree with the decision to close the other one over a fear of withdrawing consent for the code to be used.

Show me a CLA, I'll sign it and hand over rights to whatever N lines of code there are here. I am not the kind of person to back out of a legally binding agreement.