... with ::std::expm1() and ::std::log1p() of C++11

Change-Id: I0d119958152ea372c136d28705686b44b39015bf
Reviewed-on: https://gerrit.libreoffice.org/19588Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>