Better fix for FFT tests, thx to @JohanMabille
Better fix for FFT tests, thx to @JohanMabille

Turns out there was no bug in xtensor (https://github.com/QuantStack/xtensor/pull/479), I was just using it wrong, producing a dangling reference to the local variable c in the function. See http://xtensor.readthedocs.io/en/latest/closure-semantics.html#writing-functions-that-return-expressions for more info.

egpbos/xtensor-fftw,xtensor-stack/xtensor-fftw,xtensor-stack/xtensor-fftw,egpbos/xtensor-fftw