Odd length DCST-IV is inaccurate on WSL
While investigating !22 (merged) I eventually realised that the transforms using
<cmath> aren't the ones with accuracy problems. It is actually the odd-length type-IV DCT and DST that are inaccurate.
stress.py I've seen errors as large as ~1e-4 for
float which is at least 3 orders of magnitude worse than the same compiler on native linux.