Update according to vbystricky's comments

For current OpenCV-CL architecture, if the data buffer
allocated in UMat are cpu buffer(not ocl buffer) under
cpu mode, and then pass this UMat to an OpenCL kernel
as an argument, the OpenCL path will fail and fallback
to cpu mode. Take HOGDescriptor::oclSvmDetector as an example:
    ocl::setUseOpenCL(false);
    //data allocated in hog.oclSvmDetector will be cpu buffer
    hog.setSVMDetector(HOGDescriptor::getDaimlerPeopleDetector());
    ocl::setUseOpenCL(true);
    //We enabled OpenCL, but hog.oclSvmDetector are cpu buffer,
    //so it will fail in the function ocl_classify_hists
    //when reach to this line
    //idx = k.set(idx, ocl::KernelArg::PtrReadOnly(detector));
    hog.detectMultiScale(img, found, hit_threshold, win_stride,
            Size(0, 0), scale, gr_threshold);

Similar problems heppen on img_aux and img. So we should re-define
or re-set these UMat when do mode switch (CPU -> OpenCL) in order
to make their data be allocated by ocl and then OpenCL path will
succeed.
Signed-off-by: Chuanbo Weng <chuanbo.weng@intel.com>

quickly corrected the previous refactoring of features2d: moved from set(SOME_PROP, val) to setSomeProp(val)

In this particular case t shadows transpose of the base class Matx:
types.hpp:1805:14: warning: declaration of ‘t’ shadows a member of
'this' [-Wshadow]

Changelog gcc 4.8: The option -Wshadow no longer warns if a declaration
shadows a function declaration.

This warning is problematic because it prevents the module
opencv_contrib/modules/ruby to pass the build process

Merge branch 'refactor_features2d_take4' of https://github.com/vpisarev/opencv into refactor_features2d_take4

Conflicts:
	modules/features2d/src/orb.cpp

OpenCV with the refactored features2d compiles! contrib is broken for now; the tests are not tried yet