Silence -Wdeprecated-declarations for the moment

Change-Id: If08c7f72195dfff6ae3b7cb52b4137aeda3bc675
Reviewed-on: https://gerrit.libreoffice.org/6604
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>