improvements:
- Added Hann windowing and proper ring buffer (this improves visualisation significantly!)
- added mutex lock on write to fftw input buffers and fftw execute (this removes som glitches)
- improved portaudio audio input
- #370 made timeout configurable
- ncurses mode is now default again
- #379 removed key controls from noncurses to fix strange beaviour
- added config option: x-axis scale (frequency) #289
bugfixes