[ODE] auto-disable patch (yet again)

[Marco Grubert]

<< So, a patch for auto-disabling of bodies, yet again. It's here (watch
out for long links): * So, auto-disable parameters are two tresholds
(lin/ang), "idle steps"
integer, "idle time" number and a flag that can turn auto-disabling off.
These are stored in each body. Newly created bodies get these parameters
from world (so they are stored in world also, sort of "global"
parameters). There's also a helper function that sets auto-disable
parameters from world on a body. Initial auto-disable parameters in a
world are: flag=0 (auto-disable turned off), linear thr.=0.010, angular
thr.=0.008, idle steps=10, idle time=0.1. These values are from nowhere,
just worked ok in test_boxstack. >>

Thanks for the patch. I will be testing it in a few minutes.
When I tried auto-disabling a year ago I ran into the problem of a box
sliding off the edge of another box. Either the lin/ang values I picked were
too low and objects would never halt or the sliding box would stop in
mid-air because the movement was so slow. That might be a good testcase for
finding suitable values.

- Marco Grubert