Copy GpuSubtensor to the new back-end, enable its test.
Add the opt to move IncSubtensor to the new GPU back-end.
GpuIncSubtensor continued, not finished.
A first working implementation of GpuIncSubtensor.perform()

As GpuArray don't implement += and +, we pass by another interface.
remove fct not used anymore.
Advance GpuIncSubtensor c code
Finish GpuIncSubtensor c code.
Don't include Python/NumPy include, convert the string.

Otherwise, in some platform the include fail. This is more robust.
remove the import of pycuda in the new back-end.
Fix pickling of GpuIncSubtensor
Merge pull request #1664 from nouiz/gpu_inc_sub

GpuIncSubtensor