Since many elemwise ops do not call the scalar op's impl() method,
we needed to also change the perform method when numpy built-in
ufuncs are used.

Ops that are defined with upcast_to_float should upcast to
float32 or float64 minimally.

Add tests for the cases where the inputs were int8, which is when
float16 values appeared.

missing c_set_tensor4d in GpuDnnConvBase

Fixes #633

Mixed

This help gpuarray tests to run on device that don't support float64.

fix gh-2224

added op for pooling