It is now possible to call Variable.eval() with different sets of input
parameters.

Conversion of GpuSoftmax and GpuSoftmaxWithBias to the new backend

Fix unpickling of Elemwise op since openmp changes.

Tag slow tests

Don't try to use the c_code for GpuElemwise on opencl since it's cuda-only.

Replace content of c_init_code by reference to function setup_ext_cuda() in GpuSoftmax and GpuSoftmaxWithBias

Elemwise openmp

Fix Sparse grad crash and implement mixed dtype in sparse Mul/Add

I changed how format is specified. There was no bug as the input
variable are put in the key. Now I make explicit in the op key the
format.

This simplify at a few places the code too.

with and without openmp
chaced

Doc