Synopsis
		sfbilstack < in.rsf > out.rsf weight=weight.rsf verb=n niter=20 bilat=n ax= bx=

Parameters
		float ax= Gaussian weight for the range distance   bool bilat=n [y/n] if y, bilateral smoothing   float bx= Exponential weight for the domain distance   int niter=20 number of iterations   bool verb=n [y/n] verbosity   file weight= auxiliary output file name