[eigen] Missing methods for Eigen::DiagonalMatrix

[Matthias Peschke]

I recently start using the type Eigen::DiagonalMatrix but it seems that 
some methods for this type are missing. This includes the stream 
operator which is not present so that the following does not compile:

        Eigen::DiagonalMatrix<double,-1> M(10); M.setIdentity();
        std::cout << M << std::endl;
Another example is setRandom() which is not implemented and there are no 
block operations present.

Is there a special reason for this or it is because 
Eigen::DiagonalMatrix is rarely used?

Best regards,
Matthias