Adding Hatano-Nelson matrix, removing spurious Group free's in schur::SDC, adding a wrapper for MPI_Group_excl (mpi::Excl), and fixing a mistake in the distributed analytic pseudospectral calculation. During the process, bugs were seemingly uncovered in both OpenBLAS (with respect to invalid read's in the SSE2 zrot implementation) and BLIS (with respect to input matrices with zero dimensions having a null buffer).