Usage has been replaced with SvRef::get() or removed where applicable.

Change-Id: I49f108910b668466134c40940b53fc3ab2acd816
Reviewed-on: https://gerrit.libreoffice.org/29780Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>