CGS   Conjugate Gradients Squared Method.
 
    X = cgs(A,B) attempts to solve the square linear system A*X=B via
    the CGS method.
 
    This routine is simply a wrapper to Matlab's own CGS routine,
    and the argument list variations described in Matlab's CGS
    documentation are also allowed here.  The usage is identical to
    Matlab's default version, except that the first argument must be a
    Spot operator.