Purpose   
  DLACON estimates the 1-norm of a square matrix A.   
  Reverse communication is used for evaluating matrix-vector products.
Arguments   
  N      (input) INT
         The order of the matrix.  N >= 1.  V      (workspace) DOUBLE PRECISION array, dimension (N)   
         On the final return, V = A*W,  where  EST = norm(V)/norm(W)   
         (W is not returned).  X      (input/output) DOUBLE PRECISION array, dimension (N)   
         On an intermediate return, X should be overwritten by   
               A * X,   if KASE=1,   
               A' * X,  if KASE=2,
        and DLACON must be re-called with all the other parameters   
         unchanged.  ISGN   (workspace) INT array, dimension (N)
  EST    (output) DOUBLE PRECISION   
         An estimate (a lower bound) for norm(A).  KASE   (input/output) INT
         On the initial call to DLACON, KASE should be 0.   
         On an intermediate return, KASE will be 1 or 2, indicating   
         whether X should be overwritten by A * X  or A' * X.   
         On the final return from DLACON, KASE will again be 0.  Further Details   
  ======= =======
  Contributed by Nick Higham, University of Manchester.   
  Originally named CONEST, dated March 16, 1988.
  Reference: N.J. Higham, "FORTRAN codes for estimating the one-norm of 
  a real or complex matrix, with applications to condition estimation", 
ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988.