Make CV_XADD independent on STL and system headers
Avoid assert in lapac.cpp if findHomography fails in BestOf2NearestMatcher::match
add softcascade to people detector sample
Fixed MSVC warnings
Main module headers are moved 1 level up

e.g. <opencv2/core/core.hpp> become <opencv2/core.hpp>

Also renamed <opencv2/core/opengl_interop.hpp> to <opencv2/core/opengl.hpp>
Added compatibility headers
Merge pull request #640 from cuda-geek:soft-cascade-sample
Merge pull request #641 from taka-no-me:stlfree_xadd
Merge pull request #642 from taka-no-me:fix1
Merge pull request #645 from taka-no-me:bump_headers