Windows executables v1.2.0

OpenCL backend, multi-upload R2C/C2R, error handling

release: main benchmark version. Vulkan should be included in the graphics driver
Vulkan_cuFFT: requires CUDA 9. The only difference to release version is enabled cuFFT benchmark
these executables require Vulkan 1.1

CUDA_cuFFT: requires CUDA 9. CUDA backend of VkFFT

OpenCL: requires OpenCL 1.2 (lower versions are also supported but performance is not tested). OpenCL backend of VkFFT