btRaycastVehicle and btKinematicCharacterController are derived from btActionInterface now.
Some cosmetic cleanup: changed sourceforce/sf.net url to bulletphysics.com.
Please see HfFluidDemo.cpp for examples of how to use the height field fluid along with buoyant collision shapes.
The implementation is still lacking in my ways:
1) Need to complete more collision algorithms for buoyant collision shapes
2) Support compound buoyant shapes
3) The buoyancy model isn't that great
4) Fluid volume can be lost over time
