make boxfilter kernel compile on Mac GPU OCL
Add OclCascadeClassifierBuf interface
Add OpenCL stereo CSBP implementation
Fix build errors
Fix thread sync for csbp.
fix a crash on CPU OCL for some specified image sizes
Calib3d documentation:
- fixed reference to Slabaugh
Changed convexHull's documentation to essentially invert the meaning of ``clockwise``.

The orientation of convexHull's result is currently the opposite of what the
documentation would suggest:

>>> import cv2, numpy as np
>>> points = np.array([[0,0],[0,1],[1,0]], dtype=np.int32)
>>> cv2.convexHull(points, clockwise=False)
array([[[1, 0]],
       [[0, 1]],
       [[0, 0]]], dtype=int32)
>>> cv2.convexHull(points, clockwise=True)
array([[[0, 0]],
       [[0, 1]],
       [[1, 0]]], dtype=int32)

Changing the function itself is probably not a good idea at this point, so
this fixes the documentation by flipping the coordinate system.

I also removed the mention of the origin, since it's irrelevant for this
function.
Added setting feature of FPS in cap_libv4l
Optimize ocl::stereobm.
1. Use macro defines for some parameters(radius).
2. Reduce local memory usage.
3. Fix accuracy problem on Intel GPU.
Fix build
some cleanup, remove some commented codes
simplify logics in filter tests, remove redundant code in arithm tests
add copyrights
remove interpolation.hpp
further simplify the logics in filter tests
use clean EXPECT_MAT_NEAR (no string output)
Optimize stereobm a bit.
Speedup about 30% on 6730M GPU.
Fix ocl moudle build with latest Intel OpenCL SDK.
We found that cl.h file provided in latest Intel SDK muted deprecated interfaces.
fixed pca bug for fixed mean input