adder latency fft bug fix

If add latency was anything but 1, bad output would result.
Basically, default latency was being used instead of that specified.
cmult mod

Usual asynchronous mode involves a pipeline along which en travels.
For certain applications (e.g the feedback oscillator), it is more useful to have en feed every block without the pipeline.
feedback_osc bug fix

The feedback_osc requires that cmult uses a shift register style
data line (all stages shift simultaneously) instead of one at a time
as with a pipeline approach when in asynchronous mode.
coeff generation option added to fft_wideband_real

Now an option to generate coefficients using multipliers in fft_direct
instead of forced as the default.
Merge branch 'master' of github.com:ska-sa/mlib_devel