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.
Avoid obtaining several identical dimensions between two LSH sub-vectors by choosing orthogonal sub-vectors.
Fix a heap issue with static on Windows
Merge remote-tracking branch 'upstream/2.4' into LshOrthogonalSubvectors
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
1. fix an error in sample code
2. change an external link to maintain consistency with the previous tutorial
modified BackgroundSubtractorMOG2::getBackgroundImage so that it can now work with gray-level images.
remove highlighting in some function links

1. Remove whole-document highlighting in some function links
2. fix the function alias `readwriteimagevideo`
Fixed Load, Modify, and Save an Image tutorial
Keep definitions of link aliases consistent
making OCL tests conform to the comon style
disabling failing tests
Removed obsolete list from docs