Gopher Fast Fourier Transform (GFFT)

An implementation of the sparse FFT algorithms discovered by Mark Iwen described in http://www.math.duke.edu/~markiwen/DukePage/Papers/JcFFTsubmit.pdf. Used for benchmarking in http://www.ima.umn.edu/preprints/jul2010/2326.pdf. More benchmarking results will be forthcoming.