These functors were always used as unary functors with std::bind2nd.

This patch is a preparation of removal of deprecated
std::binary_function.

Change-Id: Ifd120227ab0a0db4c93dd56a9d46feb602b1ae4c
Reviewed-on: https://gerrit.libreoffice.org/39500Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>