Pick centers in KMeans++ with a probability proportional to their distance^2, instead of simple distance, to previous centers
Apply to KMeansIndex KMeanspp the same modification as in HierarchicalClusteringIndex
As some processed distances are already ^2, use template to select whether or not we have to ^2 in KMeanspp
Move templates in dist.h in order to share them between KMeansIndex and HierarchicalClusteringIndex classes.
modified OpenCL SURF API and the tests in 2.4.x to prove that it gives different from CPU results
made SURF_OCL default constructor parameters the same as SURF
modified SURF's performance test to test OpenCL version as well
fixed doc builder warnings; make sure the tests give reasonable results when OpenCL is not available
made the example consistent with the fuction definition and improved doc

made the example consistent with the fuction definition and improved doc
It's will be better
I have changed one sentence in tutorial, making it more understandable
1. fix an error in sample code
2. change an external link to maintain consistency with the previous tutorial
switching to CV_HAAR_SCALE_IMAGE mode, enabling test
modified BackgroundSubtractorMOG2::getBackgroundImage so that it can now work with gray-level images.
Libraries filter update after abs path cut.
Merge pull request #2423 from RJ2:bugfix_5
Merge pull request #2400 from RJ2:Bugfix_2
Native camera fix for some deivices with Qualcomm SoC like Samsung Galaxy S4.
adding missing include (fixing 'no ocl implementation' error)
remove highlighting in some function links

1. Remove whole-document highlighting in some function links
2. fix the function alias `readwriteimagevideo`