Do not expanding the variables in the if() clause twice, otherwise if OpenCV is
not found we end up with an error like this:

CMake Error at CMakeLists.txt:186 (if):
  if given arguments:

    "FALSE" "AND" "VERSION_GREATER" "2.4.99"

  Unknown arguments specified
--- ./CMakeLists.txt.orig      2016-03-28 21:43:04.153625000 +0000
+++ ./CMakeLists.txt   2016-03-28 21:43:15.768736000 +0000
@@ -182,7 +182,7 @@
         set(OPENCV_MIN_VERSION "2.4.9")
         DETECT_OPENCV(${OPENCV_MIN_VERSION} core highgui objdetect contrib legacy imgproc)
 
-        if(${OpenCV_FOUND} AND ${OpenCV_VERSION} VERSION_GREATER 2.4.99)
+        if(OpenCV_FOUND AND OpenCV_VERSION VERSION_GREATER 2.4.99)
             message(STATUS "ENABLE_OPENCV3 option is disabled and OpenCV >= 3.0.0 have been found. Enabled ENABLE_OPENCV3")
             set(OpenCV_FOUND FALSE)
         endif()