Count Frames Function

[kbvatral]

The count frames function currently will resort to using manual counting instead of the cv2.CAP_PROP_FRAME_COUNT property if you use version 4+ of OpenCV. From imutils/video/count_frames.py:

try:
	# check if we are using OpenCV 3
	if is_cv3():
		total = int(video.get(cv2.CAP_PROP_FRAME_COUNT))

	# otherwise, we are using OpenCV 2.4
	else:
		total = int(video.get(cv2.cv.CV_CAP_PROP_FRAME_COUNT))

I believe that if OpenCV 4 using the same property as OpenCV 3, so this should be as simple as changing the if statement to check if cv3 or cv4. Is there already a convenience function for checking version 4 that could be used here?