The OpenCL tests seems like a duplicate of the compositions tests, opencl and
cpu code should produce identical results; anything else is a failure - for
testing opencl it would be better to rig the composition tests to run twice
once with opencl enabled and once with opencl disabled.

Ideally we would want to be using the built in sample compositions of
operations that produce the gallery of operations for testing as well, and
get rid of the quite manual procedures involved in adding new tests to the
current framework.