Problem source:
Qualified names (aka QName) didn't work as tag names and attribute names,
because the parser lacked a real rule to scan QName, so it understood
only non-qualified names without prefixes.

Solution:
New rule was added to check both "ident" and "ident:ident" sequences.


mysql-test/r/xml.result:
  Adding test case
mysql-test/t/xml.test:
  Adding test case
sql/item_xmlfunc.cc:
  Adding real QName parser rule and using it in NodeTest rule.