opencv: Bug compiling with CUDNN with 4.1.2

https://github.com/opencv/opencv/archive/4.1.2.zip

This version has a bug when compiling for CUDNN. File cmake/FindCUDNN.cmake is faulty and needs two corrections:

1. location of libcudnn library is searched in the wrong file. It is seached in cudnn.h while it is in cudnn_version.h
2. The “set” creating the CUDNN version has a problem and needs to be modified.

In file cmake/FindCUDNN.cmake
Replace:
  file(READ "${CUDNN_INCLUDE_DIR}/cudnn.h" CUDNN_H_CONTENTS) 
With:
  file(READ "${CUDNN_INCLUDE_DIR}/cudnn_version.h" CUDNN_H_CONTENTS)

And replace:

set(CUDNN_VERSION
   "${CUDNN_MAJOR_VERSION}.${CUDNN_MINOR_VERSION}.${CUDNN_PATCH_VERSION}"
   CACHE
   STRING
   "cuDNN version"
 )

# with:
 set(CUDNN_VERSION
   "${CUDNN_MAJOR_VERSION}.${CUDNN_MINOR_VERSION}.${CUDNN_PATCH_VERSION}"
 )

And now it compiles correctly.

 cmake \
 -D CMAKE_BUILD_TYPE=RELEASE \
 -D WITH_CUDA=ON \
 -D WITH_CUDNN=ON \
 -D OPENCV_DNN_CUDA=ON \
 -D CUDA_ARCH_PTX="" \
 -D CUDA_ARCH_BIN="5.3,6.2,7.2" \
 -D WITH_CUBLAS=ON \
 -D WITH_LIBV4L=ON \
 -D BUILD_opencv_python3=ON \
 -D BUILD_opencv_python2=OFF \
 -D BUILD_opencv_java=OFF \
 -D WITH_FFMPEG=ON \
 -D WITH_GSTREAMER=ON \
 -D WITH_TBB=ON \
 -D BUILD_TBB=ON \
 -D WITH_GTK=ON \
 -D BUILD_TESTS=OFF \
 -D BUILD_PERF_TESTS=OFF \
 -D BUILD_EXAMPLES=OFF \
 -D OPENCV_EXTRA_MODULES_PATH=../../opencv_contrib-4.1.2/modules \
 ..