Modified to test non-contiguous innermost stride, checked entire domain, expanded to 4D.
Added declarations for cuMemcpy3D.
Used clEnqueue(Read/Write)BufferRect for the 2 innermost dimensions of a copy.
A few small debug checks/info.
Merge branch 'gpu_non_contiguous_copies' of https://github.com/halide/Halide into gpu_non_contiguous_copies
Added debug output for outer dimensions in copies.
Made test run on smaller subset to avoid very large numbers of copies.