unnecessarily passing primitives by const ref.

Suggested by Tor Lillqvist

Change-Id: I445e220542969ca3e252581e5953fb01cb2b2be6
Reviewed-on: https://gerrit.libreoffice.org/24672Reviewed-by: Tor Lillqvist <tml@collabora.com>
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>