modified BackgroundSubtractorMOG2::getBackgroundImage so that it can now work with gray-level images.
Merge branch '2.4' of git://github.com/Itseez/opencv into mog2_bgimg_gray
made a performance improvement.
changed the way the mean value for each pixel is assigned in the output image.
Bugfix #3668 in FilterEngine::apply(), use the ROI properly
Bugfix #3668 removed the comment
doc: update/clarify behaviour of mask in floodFill

Clarify how the mask parameter is set on output and how this is
affected by the flags parameter.

resolves Feature #2942
fix cv::kmeans function

reshape input matrix, since the function works with data
as with [N x dims] matrix
use more accurate reshape
add additional tests for different input cases
fix coordinate problem with large images - bug 1523
Merge pull request #2744 from jet47:kmeans-fix
Merge pull request #2738 from kevmitch:2.4
Merge pull request #2739 from StevenPuttemans:bug_1523
Merge pull request #2701 from thoinvil:BugfixFilterEngineApplyROI
Merge pull request #2509 from euphrat:mog2_bgimg_gray