DMDetector: improve debugging output
DMDetector: improve debugging output

huycn/zxing-cpp,huycn/zxing-cpp,nu-book/zxing-cpp,nu-book/zxing-cpp,huycn/zxing-cpp,huycn/zxing-cpp,nu-book/zxing-cpp,huycn/zxing-cpp,huycn/zxing-cpp,nu-book/zxing-cpp,nu-book/zxing-cpp,nu-book/zxing-cpp,nu-book/zxing-cpp,nu-book/zxing-cpp,huycn/zxing-cpp,huycn/zxing-cpp