MultiThreaded Demo:

- fixing various race conditions throughout (usage of static vars, etc)
 - addition of a few lightweight mutexes (which are compiled out by default)
 - slight code rearrangement in discreteDynamicsWorld to facilitate multithreading
 - PoolAllocator::allocate() can now be called when pool is full without
     crashing (null pointer returned)
 - PoolAllocator allocate and freeMemory, are OPTIONALLY threadsafe
     (default is un-threadsafe)
 - CollisionDispatcher no longer checks if the pool allocator is full
     before calling allocate(), instead it just calls allocate() and
     checks if the return is null -- this avoids a race condition
 - SequentialImpulseConstraintSolver OPTIONALLY uses different logic in
     getOrInitSolverBody() to avoid a race condition with kinematic bodies
 - addition of 2 classes which together allow simulation islands to be run
   in parallel:
    - btSimulationIslandManagerMt
    - btDiscreteDynamicsWorldMt
 - MultiThreadedDemo example in the example browser demonstrating use of
   OpenMP, Microsoft PPL, and Intel TBB
 - use multithreading for other demos
 - benchmark demo: add parallel raycasting

src/BulletCollision/CollisionDispatch/btCollisionObject.h

@@ -79,6 +79,7 @@ protected:
 
 	int				m_islandTag1;
 	int				m_companionId;
+    int             m_uniqueId;
 
 	mutable int				m_activationState1;
 	mutable btScalar			m_deactivationTime;
@@ -455,7 +456,17 @@ public:
 		m_companionId = id;
 	}
 
-	SIMD_FORCE_INLINE btScalar			getHitFraction() const
+    SIMD_FORCE_INLINE int getUniqueId() const
+    {
+        return	m_uniqueId;
+    }
+
+    void	setUniqueId( int id )
+    {
+        m_uniqueId = id;
+    }
+
+    SIMD_FORCE_INLINE btScalar			getHitFraction() const
 	{
 		return m_hitFraction; 
 	}