Copied errorCovPre to errorCovPost. This allows the correct behaviour of the uncertainty to grow when there is missing data for each predict step.
Added few opencl optimizations (as Intel platform codepath):

1. HaarDetetctor: repack nodes to reduce memory footprint
2. cornerMinEigVal: 4 ocl kernels are fused into 1 for sobel calculation
try to fix build error
try to made compatible with mac
rename imageproc_sobel2.cl -> imageproc_sobel3.cl for consistency
fix bugs on host and device sides for imgprog_sobel3.cl
Fix a typo
fixed find package CUDA for cross-compilation

replaced find_host_package with find_package and
set CMAKE_FIND_ROOT_PATH_MODE_LIBRARY to BOTH, because NEVER 
doesn't work for CUDA_CUDA_LIBRARY, which is located in 
/usr/arm-linux-gnueabihf/lib/libcuda.so for ARM
Merge pull request #1713 from pengx17:patch-2
Merge pull request #1675 from krodyush:opencl-optimization
Merge pull request #1714 from jet47:find-cuda-fix
ocl: split: update tests and implementation
Merge pull request #1652 from nghiaho12:kalman
Merge pull request #1712 from alalek:ocl_split