According to the documentation "Run-time GCD & LCM Determination": [1],
gcd should be consumed from boost::math::gcd.

[1] <http://www.boost.org/doc/libs/1_64_0/libs/math/doc/html/math_toolkit/run_time.html>

Change-Id: I026a4e8ead75399765eb73fa5434a57958676383
Reviewed-on: https://gerrit.libreoffice.org/37260Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>