fix gh-1381 c linker crash with not used inputs.

Document how to add scalar op and random number distribution.

Fix typos, some rephrasing.

make EquilibriumOptimizer use a dict to map ops to their nodes rather than running everything on everything.

list() the iterator for local_optimizers

replacing the test id (module path and fct name) with the first line
of the docstring, making it hard to identify what version of the test
failed.

This is mostly for tests that are shared between tensor and cuda/gpuarray.

Fix crash in python 3 recently inserted.

Remove Rebroadcast in the input of Join.

Add it only when needed in the grad.

Fix other crash in hessian of stack()

mod derivative

Fixes in downsample.py for python 3

Few changes to mod derivative

Add c code to rebroadcast.