ExtractValue didn't understand tag and attribute names
consisting of "tricky" national letters (e.g. latin accenter letters).
It happened because XPath lex parser recognized only basic
latin letter a..z ad a part of an identifier.

Fixed to recognize all letters by means of new "full ctype" which
was added recently.


mysql-test/r/xml.result:
  Adding test case
mysql-test/t/xml.test:
  Adding test case
sql/item_xmlfunc.cc:
  Using recently implemented "true" ctype functionality
      to treat all national letters as valid tag names,
      Only basic latin letters worked so far.
strings/ctype-simple.c:
  A bug fix: ctype is array of 257 elements,
      adding offset to address correct element.