Enable OpenCL version of norm and convertScaleAbs or 32F data

Fix error in minmaxloc.cl
Change test for convertScaleAbs
Fix minMaxIdx for _src2 align
Change epsilon on the tests
Change epsilon for NORM_INF_2args accuracy tests
Set sync=true in ocl_minMaxIdx kernel call. For tests
Disable OpenCL version of minMaxIdx with mask on AMD devices
Merge pull request #3088 from vbystricky:ocl_enableNormEtc
Set status to alpha
Merge tag '3.0.0-alpha'

OpenCV 3.0.0 Alpha
Merge pull request #3106 from LeszekSwirski:fix-gemm-buf-allocate