support OpenCV4 for simplepose example (#1391)

examples/simplepose.cpp

@@ -19,6 +19,11 @@
 #include <opencv2/highgui/highgui.hpp>
 #include <opencv2/imgproc/imgproc.hpp>
 
+#if CV_VERSION_MAJOR >= 4
+#include <opencv2/opencv.hpp>
+#define CV_LOAD_IMAGE_COLOR cv::IMREAD_COLOR
+#endif  // CV_VERSION_MAJOR >= 4
+
 #include "net.h"
 #include "gpu.h"