[ODE] more c++, auto-enabling

[Matthew D. Hancher]

> live .. not having this behavior would raise all sorts of tricky
> questions, like what happens to a live body when it is connected by a
> joint to a dead body. if the dead body behaves as though it was a live

Oh right, my brain was disengaged this morning.  I was not thinking
at all about what island-solving might look like with disabled bodies.
Righty-o.

Speaking of which, the core solver is the las bit of code I want to
read and understand, as I try to finish coming up to speed on ODE.
(Well, all the trimesh stuff too, but I'm not using that right now
anyway.)  I have a basic understanding of linear complementary
problems, but I'd like to bone up a bit on the theory and numerical
algorithms as I read the code.  I've followed the obvious links
online, which look reasonable and will do in a pinch, but does anybody
have any suggestions of papers or books they've found to be
particularly enlightening?

Also, does anybody know what Newton Game Dynamics is really talking
about when they mention their "deterministic solver, which is not
based on traditional LCP or iterative methods"?

mdh