* tests/binarization/sauvola_ms.cc,
	* tests/binarization/sauvola_ms.ref.pbm,
	* tests/binarization/sauvola_ms_weven_hodd.ref.pbm,
	* tests/binarization/sauvola_ms_wodd_heven.ref.pbm,
	* tests/binarization/sauvola_ms_wodd_hodd.ref.pbm: Make use of
	reference files in test.