Add ocl's good features to track implementation.
Additional notes with this commit:
1. Add cornerHarris_dxdy and cornerMinEigenVal_dxdy to get
the interim dx and dy output of Sobel operator;
2. Add minMax_buf to allow user to reuse buffers in minMax;
3. Fix an error when either min or max pointer fed into minMax is NULL;
4. Corner sorter temporarily uses C++ STL's quick sort. A parallel
 selection sort in OpneCL is contained in the implementation but disabled
due to poor performance at the moment.
5. Accuracy test for ocl gfft.
add two samples
remove the images in ocl sample folder
add results verification to facedetect and hog samples
android -> plarforms/android
Build fixes. Build scrips reorganized.
Fix a bug when pushing pointers of arguments into std::vector.
When argument pointers pushed into an vector and the pointers point to
address on stack, we need to make sure they are valid until kernels are
successfully flushed onto the queue.
revise perf
Fix 2.4 ocl Canny.
This fix is a workaround for current 2.4 branch without introducing an
additional oclMat buffer into CannyBuf object.
Test case is cleaned up.
Volatile keywords in kernels are removed for performance concern.
adjust test cases
fixing #3027 (searching JNI even if no ant), fixing java tests status message (ON/OFF)
Merge branch '2.4' of https://github.com/Itseez/opencv into 2.4_oclgfft
Merge pull request #910 from pengx17:2.4_oclgfft
Merge pull request #920 from asmorkalov:android_move
Merge pull request #928 from apavlenko:bugfix_3027
Add non-stump based ocl Haar cascade classifier support.
For example, haarcascade_frontalface_alt2.xml is now supported.
Note that classifier's pattern of a cascade file must be consistent,
i.e., all trees must either have two nodes or one node, otherwise
unexpected results will occur.

Other fixes:
Test cases are updated.
Some unused codes are removed.
Fix some problems of haar when using OclCascadeClassifierBuf.
Fix brute_force_matcher's hung on some Intel CPU OCL
Merge pull request #930 from pengx17:2.4_haar_ext
Merge pull request #927 from bitwangyaoyao:2.4_perf
Merge pull request #925 from pengx17:2.4_canny_tmp_fix