diff icons/zoom-out.png @ 146:d27f13651e67

* don't store fft values scaled by fftsize/2; that's a special requirement
  for the spectrogram, and other applications will not expect it -- make the
  spectrogram do that scaling itself
* add a higher-resolution memory cache (still polar, though) as an alternative
  to the 16-bit compact cache
* don't use the memory cache if we want rectangular coords (unless the disc
  cache is totally infeasible) as conversion slows it down anyway
* avoid redundant rectangular -> polar -> rectangular conversion when storing
  values in a rectangular-mode disc cache