which had served since d441fa1f;
we now have polymorhpic std::abs.

Change-Id: Ibe48ac51508f7d9f5a44d712550237db7f553df3
Reviewed-on: https://gerrit.libreoffice.org/32225Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
Tested-by: Stephan Bergmann <sbergman@redhat.com>