Updated World.Step Function

        /// <summary>
        /// Take a time step. This performs collision detection, integration,
        /// and constraint solution.
        /// </summary>
        /// <param name="dt">The amount of time to simulate, this should not vary.</param>
        public void Step(float dt)
        {
#if (!SILVERLIGHT)
            if (Settings.EnableDiagnostics)
                _watch.Start();
#endif

            ProcessChanges();

#if (!SILVERLIGHT)
            if (Settings.EnableDiagnostics)
                AddRemoveTime = _watch.ElapsedTicks;
#endif

            // If new fixtures were added, we need to find the new contacts.
            if ((Flags & WorldFlags.NewFixture) == WorldFlags.NewFixture)
            {
                ContactManager.FindNewContacts();
                Flags &= ~WorldFlags.NewFixture;
            }

            // Update contacts. This is where some contacts are destroyed.
            ContactManager.Collide();

#if (!SILVERLIGHT)
            if (Settings.EnableDiagnostics)
                ContactsUpdateTime = _watch.ElapsedTicks - (AddRemoveTime + ControllersUpdateTime);
#endif

            //If there is no change in time, no need to calculate anything.
            if (dt == 0 || !Enabled)
            {
#if (!SILVERLIGHT)
                if (Settings.EnableDiagnostics)
                {
                    _watch.Stop();
                    _watch.Reset();
                }
#endif
                return;
            }

            TimeStep step;
            step.inv_dt = 1.0f / dt;
            step.dt = dt;
            step.dtRatio = _invDt0 * dt;

            //Update controllers
            for (int i = 0; i < ControllerList.Count; i++)
            {
                ControllerList[i].Update(dt);
            }

#if (!SILVERLIGHT)
            if (Settings.EnableDiagnostics)
                ControllersUpdateTime = _watch.ElapsedTicks - AddRemoveTime;
#endif

            // Integrate velocities, solve velocity raints, and integrate positions.
            Solve(ref step);

#if (!SILVERLIGHT)
            if (Settings.EnableDiagnostics)
                SolveUpdateTime = _watch.ElapsedTicks - (AddRemoveTime + ControllersUpdateTime + ContactsUpdateTime);
#endif

            // Handle TOI events.
            if (Settings.ContinuousPhysics)
            {
                SolveTOI(ref step);
            }

#if (!SILVERLIGHT)
            if (Settings.EnableDiagnostics)
                ContinuousPhysicsTime = _watch.ElapsedTicks -
                                        (AddRemoveTime + ControllersUpdateTime + ContactsUpdateTime + SolveUpdateTime);
#endif
            _invDt0 = step.inv_dt;

            if ((Flags & WorldFlags.ClearForces) != 0)
            {
                ClearForces();
            }

            for (int i = 0; i < BreakableBodyList.Count; i++)
            {
                BreakableBodyList[i].Update();
            }

#if (!SILVERLIGHT)
            if (Settings.EnableDiagnostics)
            {
                _watch.Stop();
                //AddRemoveTime = 1000 * AddRemoveTime / Stopwatch.Frequency;

                UpdateTime = _watch.ElapsedTicks;
                _watch.Reset();
            }
#endif
        }