BulletSim: add inTaintTime parameter to collision cache clear function.
BulletSim: a better version of llMoveToTarget that doesn't go crazy.
There is still some overshoot but mostly fixes Mantis 6693.
Fix bug where moveToTarget was active for non-physical objects
and while selected.
Fix bug where move target was not getting changed if the script
changed the target during a move.
BulletSim: set linkset type to be prim specific rather than a simulator
wide default. This allows individual prims to differ in the
underlying linkset implementation.
BulletSim: remove the handle to the vehicle actor and cause routines
that need it to look it up.