* Implement other stepping methods from well-known packages such as
RKSUITE, etc

* Provide the bsimp method with a way to back out of its internal
subdivision algorithm when this blows up.  In the internal steps the
solution is advanced by an iteration involving terms like (inv A)^n,
where n can be O(10-100), which can easily overflow.  It should be
possible to check for this and back out of it to the previous level of
subdivision by returning GSL_EFAILED instead of GSL_SUCCESS.  For an
example try solving the demo.c Van der Pol oscillator with bsimp.
