improve resampler and/or gaussian?

[nyanpasu64]

samples are a bit more muffled than they should be even with -g.

• cymbal playing at near-exactly 32000khz (spc700 steps by 1 sample) is muffled compared to 44100khz (step by >1)
  • unsure how much can be done, considering the snes gaussian changes frequency response depending on phase,
• wavetable sweep sounds quite muffled at 192 samples long, despite fine on n163

[nyanpasu64]

The resampler is pretty bad.

• when downsampling in bandlimited mode, audio significantly above the output's Nyquist rate is folded instead of silenced.
• On some samples, resampling a properly looped (but possibly non-multiple-of-16) sample leads to a loud pop when the .brr loops (the sample is not looped properly).