Memory leak in platform/fft-pffft.h

[hgroenenboom]

Hi,

First of thanks for the beautiful timestretch library! I've been using signalsmith-stretch with pffft and noticed a memory leak.

When Pow2FFT is destroyed it uses resize(0) to free up memory but it seems pffft (at least the pffft version I am using) always allocates memory even if size is 0:
https://github.com/marton78/pffft/blob/a4b03590cc2a4bea56f9721996e3057835799179/src/pffft_common.c#L10

I fixed this localy with

~Pow2RealFFT() {
	if (hasSetup) pffft_destroy_setup(fftSetup);
	if (work) pffft_aligned_free(work);
	if (tmpAligned) pffft_aligned_free(tmpAligned);
}

I think other.fftSetup = nullptr;is missing from the move constructor as well