This not only avoids all the overhead of i18npool's TextSearch and
Transliteration efforts (which are useful in the Find&Replace
dialog bu we don't use here) that could possibly even get in the
way how they are implemented, but also gives us direct control
over all possible flags; plus ICU's replace features are more
convenient to use and have better error checking to report back
and there is the advantage that ICU's regex description can be
taken verbatim.

Change-Id: Iaa06c26a3ff6882a0057d1ca92b1605073429bca
Reviewed-on: https://gerrit.libreoffice.org/62531Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>