Function decompose_schur_3 

pub fn decompose_schur_3<S>(h: UpperHessenberg3<S>) -> (Matrix3<S>, Matrix3<S>)
where
    S: Real + AbsDiffEq<Epsilon = S>,

Returns matrices (q, u) of the decomposition h = quq^{-1} where q is an orthogonal matrix and u is an upper quasi-triangular matrix