Use log scale for visualizer (#397)

* Visualizer: use log scale

- log scale frequency and gain
- Hamming windowing
- improve reading from fifo

* Fix Visualizer memory leaks

* Visualizer: use Blackman window

* Visualizer: support DFT zero padding

* Visualizer: support fractional height bars, fix fifo read

* Revert "Fix Visualizer memory leaks"

This reverts commit 5c6509d2b8ed985a4928f681217dc8616d053ace.

* Visualizer: fix fifo read again

* Visualizer: add cubic interpolation option

* Visualizer: Expose more config options, add docs for config options

* Visualizer: Use reverse video text for stereo visualizer smooth look

* Visualizer: use FormattedColor to for reverse-video

* Visualizer: change some config options for spectrum

* Fix build fftw disabled

* Visualizer: use [0,5] interval for dft_size config option

src/settings.h

@@ -82,6 +82,11 @@ struct Configuration
 	std::string lastfm_preferred_language;
 	std::wstring progressbar;
 	std::wstring visualizer_chars;
+	bool visualizer_autoscale;
+	bool visualizer_spectrum_smooth_look;
+	uint32_t visualizer_spectrum_dft_size;
+	double visualizer_spectrum_hz_min;
+	double visualizer_spectrum_hz_max;
 
 	std::string pattern;