Import fftconv.py with some pep8 modifications.

This comes from Sander Dieleman <sanderdieleman@gmail.com> (@benanne on github).

Import fftconv.py with some pep8 modifications.
9aa65181 · Arnaud Bergeron · 2993e6f7 · 9aa65181
--- a/theano/sandbox/cuda/fftconv.py
+++ b/theano/sandbox/cuda/fftconv.py