The test was using vloada_half which does not exist for scalars.
Also removed the files test.vloada_half_*.* from half.zip.
For test.vloada_half3_global, changed the OpenCL kernel to use
vload_half instead of vloada_half.
Build failures will return a proper failure now, before, the test was
passing in this case.
More Info: https://github.com/KhronosGroup/OpenCL-Docs/issues/648