don't use deprecated MappedSparseMatrix
This MR removes Eigen-internal references to the deprecated MappedSparseMatrix type. Q: should the MappedSparseMatrix type be removed entirely, now that the C++14 jump is happening?
This MR removes Eigen-internal references to the deprecated MappedSparseMatrix type. Q: should the MappedSparseMatrix type be removed entirely, now that the C++14 jump is happening?