fi() replacement script

fi() is used in certain places to generate and pack coefficients in BRAMs.
Unfortunately this is part of an add-on to Matlab. This script
can be used instead.
fi() removal in fft family

twiddle factors were generated using fi(). Replaced with calls to
doubles2unsigned. Basic simulations performed, more rigorous testing
required.
Merge branch 'master' of github.com:ska-sa/mlib_devel