Display non-ascii chars in PKP tickets

PKP uic codes encode non-ascii letters as <number>, where number
corresponds to a Polish letter.  While I did not reverse-engineer it
fully, from the available samples I am quite sure that at least the
uppercase letters are correct (and the rest matches alphabetical
ordering).

This commit addresses the problem partially fixed by
c2962fe8 ("Improve PKP extractor script")
but (more) fully this time.