Update to 1.22

Upstream changes:
1.22  Sat Nov 11 10:53:35 2017
    - someone suggests using 'exists' for checking the truth of
      $collator->{mapping}{$variable} and $collator->{maxlength}{$variable},
      where $variable may stand for codepoints whose mapping is not defined;
      though such a problem was not reproduced on my environment.

(wen)