LSSVD:

--------------------------------------------------------------------------
   Solves ax = b using the singular value decomposition

   Since version 1.
--------------------------------------------------------------------------
   Form:
   [x, r, cn, rank] = LSSVD( a, b, tol )
--------------------------------------------------------------------------

   ------
   Inputs
   ------
   a                  A matrix
   b                  Right-hand-side
   tol                Tolerance on the minimum singular value

   -------
   Outputs
   -------
   x                  State
   r                  Residual Ax - b
   cn                 Condition number
   rank               Rank of the matrix

--------------------------------------------------------------------------
    References: Forsythe, G.E., M.A. Malcolm, C.B. Moler, Computer Methods
                for Mathematical Computations, Prentice-Hall, 1977,
                 pp. 192-213.
--------------------------------------------------------------------------