Fix and update to more recent gpu_fft lib

[colin-guyon]

Hi, your code was almost working, I fixed only minor things. The cython code could be optimized fixing types of input vars for example.

[pguillem]

Any updates on this lib?

[colin-guyon]

No it does not seem, but if you want another example of the gpu_fft lib used from python using cython you can check https://github.com/colin-guyon/rpi-audio-levels

[pguillem]

Thanks colin!
I will give it a try right away.

I was actually trying to compile from the original GPU_FFT project, but it seems either i´m missing some gcc flags of the code itself has something missing. I kept getting undefined symbol errors and it wouldn´t import the gpu_fft header files.