Run OpenCL unit tests on Windows

[ihhub]

Currently we don't run OpenCL compiled unit tests on AppVeyor due to runtime error in the application. The possible issue of the application crash could be in CUDA package usage. Other projects which use OpenCL are able to run OpenCL compiled applications. We might just need to separately install OpenCL package to avoid the crash.

[ihhub]

Here is a potential solution for OpenCL (was taken from compute project):

before_build:
  # Install OpenCL headers and libraries
  - set NUGETDIR=C:\NUGET
  - nuget install opencl-nug -Version 0.777.77 -OutputDirectory %NUGETDIR%
  - dir %NUGETDIR%\opencl-nug.0.777.77\build\native\
  - set OCL_ROOT=%NUGETDIR%\opencl-nug.0.777.77\build\native
  # Install OpenCL Runtime
  - choco install opencl-intel-cpu-runtime
  # Check if it's working
  - ps: appveyor DownloadFile "https://ci.appveyor.com/api/projects/oblomov/clinfo/artifacts/clinfo.exe?job=platform:+x64" -FileName clinfo.exe
  - .\clinfo.exe

[ihhub]

@yannlabou what do you think about it?