SUDIFF, SUSUM, SUPROD, SUQUO, SUPTDIFF, SUPTSUM,
 SUPTPROD, SUPTQUO - difference, sum, product, quotient of two SU data
                     sets via suop2

 Usage:
 sudiff file1 file2 > stdout
 susum file1 file2 > stdout
 ...etc

 Note: uses   suop2  to perform the computation