integrating opensim-git commit abf85b7f192e167ed5f462ac8d1a8de365e4f03b:

[PATCH] Bulletsim: Create AvatarTerminalVelocity to BulletSim like
 what ODE and SL has. Before this falling from really high
 caused the avatar to fall faster then the viewer can handle
 and cause camera issues.

Signed-off-by: ft <ft@noemail>