Generate an n-point gaussian convolution window
w = moc_gaussian (n, a)
Generate an n-point gaussian convolution window of the given width. Use larger a for a narrower window. Use larger n for longer tails.
w = exp ( -(a*x)^2/2 )
for x = linspace ( -(n-1)/2, (n-1)/2, n ).
Width a is measured in frequency units (sample rate/num samples). It should be f when multiplying in the time domain, but 1/f when multiplying in the frequency domain (for use in convolutions).