[MRG]Gpua eye

Do not merge yet.

I want to make an include in compyte called compyte_cuda.h, that will have inline fct to replace some CudaNdarray macro, for example to replace CUDANDARRAY_DEV_DATA that will do the hack to get the ptr and add the offset.

That way the first conversion will be faster to the other op.

@abergeron, can you review this PR? How can I assert the the back-end used if cuda in the c_code make_node fct?