testing: fftw now shared bins single + double precision

There was an request for a shared version of fftw and on the way of changing it, with input from archer Thomas Ebi and looking at some debian and slackware configs, i made a new fftw, that is now shared and contains single (float) and double precision versions of the binary in the package. As such changes need testing, i've put it to testing and will keep it a week there so that any trouble can be found and corrected before it goes to [extra].