Copy the old GpuConv to the new back-end.
Advance the new GpuConv
new GpuConv compile, but give wrong version in some cases!
make sure the input var are of the right type.
First pass at type safety in printfs.
Clean up types in printfs to make sure the printouts will work on 32 and 64 bits machines.
Fix GpuArrayType.values_eq_approx(). It wasn't checking the signe correctly.
pep8
implement GpuArrayType.values_eq_approx() parameter atol and rtol.

Make the gpuarray opt for conv use it.
remove deprecated comment
pep8
Fix crash in the new gpuconv opt. Make it reuse op_lifter
Use the good type.
Merge pull request #1668 from nouiz/gpu_conv

port GpuConv to the new gpu back-end