fix release build

.gitignore

@@ -25,3 +25,4 @@ Test*.cpp
 # executables
 /lines
 unittest_*
+gmon.out

lines.cpp

@@ -128,7 +128,9 @@ int main(int argc, char *argv[])
 	}
 	//dotwidth is just a simple size so that lines and dots are visible on big images
 	//but not huge on small images
+#ifdef _DEBUG
 	unsigned short dotwidth = img.cols >> 6;  // divide by 64, so efficient
+#endif
 
 	std::vector< std::vector<cv::Point> > contours;
 	std::vector<cv::Vec4i> hierarchy; //this is not really useful