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