Update the OpenCL documents.
fix three warning about mog, mog2 and KNearestNeighbour.
fix warning about addWeighted and remove magnitudeSqr().
fix for bug #3291:

add INSTALL command for TBB target
Missing closedir with opendir
Add opencl svm.
fix build error
Fix new blank line at EOF.
Merge pull request #1522 from nghiaho12:latentsvm
Merge pull request #1518 from jet47:bug-3291-tbb-install
Merge pull request #1509 from perping:2.4_docs
Merge pull request #1457 from pengx17:2.4_oclsvm