Plumb the connection through from llSetVehicleFloatParam

to the various physics engines. No connection to the 
underlying physics simulator yet, just plumbing through
the various classes.

OpenSim/Region/Physics/POSPlugin/POSCharacter.cs

@@ -159,6 +159,12 @@ namespace OpenSim.Region.Physics.POSPlugin
             set { return; }
         }
 
+        public override float VehicleFloatParam
+        {
+            get { return 0f; }
+            set { return; }
+        }
+
         public override PhysicsVector CenterOfMass
         {
             get { return PhysicsVector.Zero; }