Support for unicode characters

[aeschli]

From microsoft/vscode#7115:
The following xml content is not colorized correctly:

<?xml version="1.0" encoding="utf-8" standalone="no" ?>
<WorkFine>
  <NoColorWithNonLatinCharacters_АБВ NextTagnotWork="something" Поле="tagnotwork">
     <WorkFine/>
     <Error_АБВГД/>
  </NoColorWithNonLatinCharacters_АБВ>
</WorkFine>