Helocut - Helix Lowcut filter in 2-D

Helocut < in.H helix=1 na=16 eps=0.1 > out.H

Applies helix convolution with a low-cut factor, based on factoring the laplacian filter. Also loops over n3.

from history	integer	n1 , n2
from par	logical	helix =1	if 0, apply the gradient filter on the 1st axis
	real	eps	sets the lowcut frequency
	integer	na =16	filter size (half the number of nonzero coefficients)

Modules: helicon.lop , helocut.r90