implemented umat expressions
added perf test
condition for Mat step
added cv::sqrBoxFilter to T-API
fixing issues from coverity scan 1167937, 1167938, 1167939, 1127248 (http://scan.coverity.com/projects/169?tab=Overview)
Merge pull request #2289 from ilya-lavrenov:umat_expr
Merge pull request #2287 from ilya-lavrenov:mat_step
Merge pull request #2251 from ilya-lavrenov:tapi_sqrboxfilter
ocl: workaround for failures with misaligned host buffers
ocl: update gftt
Merge pull request #2296 from apavlenko:fix_coverity_scan
Merge pull request #2295 from alalek:opencl_align_rw_buffers
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  ocl: update gftt
  ocl: workaround for failures with misaligned host buffers
  fixing issues from coverity scan 1167937, 1167938, 1167939, 1127248 (http://scan.coverity.com/projects/169?tab=Overview)
  added cv::sqrBoxFilter to T-API
  condition for Mat step
  added perf test
  implemented umat expressions