Further optimize the implementation of Hermite Normal Form in Sage
PEOPLE: Clement Pernet, William Stein
SUMMARY: Do the following:
- Rewrite add row to (a) use a block method, and (b) use fast non-recursive code (it is silly right now).
- Implement (or wrap?) Clement's "twice as fast" double det.
ISSUES: Building Linbox's rational solver is currently broken on some platforms.