strict mode to avoid nested scan

R op for Conv2d

[CRASH] Fix scan_op.connection_pattern and add test

Conflicts:
	theano/tests/test_rop.py

Conflicts:
	theano/tensor/nnet/conv.py

Fix typos in new cudnn v2 blurb

[CRASH ] Fix crash in scan.grad when same variable used for multiple outputs

Raise an error if cudnn v2 rc* are used.

fix code samples in debug_faq docs

- fixed the order of arguments in an isinstance() function call
- changes the expected output of a command to match the actual output

cudnn doc update.

Add connection_pattern

Apply decorator for stochastic tests on test_run_nnet

Add (zero) gradient for any() and all().

Python3 compatibility.