Hi - not sure if anything but i.fft uses this, but FYI..
There's a new stable version of the fftw Fourier transform package just out:
http://www.fftw.org/
FFTW v3.0
* Speed: often 20% or more faster than FFTW 2.x,
* the API is incompatible to previous versions
ftp://ftp.fftw.org/pub/fftw/NEWS
the libaries are now named:
libfftw3.a
libfftw3.la
includes:
fftw3.f
fftw3.h
and symlinking to the old names doesn't work 
Hamish