started replacing libFFTW3 with a custom DFT/FFT implementation
	reduce external dependencies

libFFTW3 now hopefully obsolete
	using a small FFT implementation from KLib

added CMake build for the KSynth backend
	mainly to run some test-cases and performance benchmarks

added a more spectrum-correct square-wave
	this should reduce aliasing effects

fixed some simple synth issues
	wrong FM calculation
	some performance enhancements
		maybe switching to INTs as IDX improves performance further due to LUT?