Define __ne__ as "not equal" by default in PureOp.

finish gh-2768

[MRG] Faster test

Fix condition in equal_computations

Fix how some tests get a reference to scan nodes in a theano function

[CRASH new backend] Fix comparison between ssize_t and size_t

Mixed: more error detection, clean up, optimization

Fix syntax error.

[CRASH] add check to ensure that first input is HostFromGpu in gpuarray/local_assert

Fix some different behavior depending with not default mode.

Register local_remove_all_assert

[REGRESSION, CRASH]Fix crash gpu

[CRASH with Scan in new backend]