support diamondsubdivision (thanks Jay for contribution)

support user-defined broadphase collision filtering (thanks Marten)
make sure btSimpeDynamicsWorld doesn't use cache friendly optimization in the solver (added an assert, and updated BasicDemo)

src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.h

@@ -38,6 +38,7 @@ protected:
 	
 	bool	m_useFloatData;
 	bool	m_flipQuadEdges;
+  bool  m_useDiamondSubdivision;
 
 	int	m_upAxis;
 	
@@ -62,6 +63,8 @@ public:
 	virtual ~btHeightfieldTerrainShape();
 
 
+	void setUseDiamondSubdivision(bool useDiamondSubdivision=true) { m_useDiamondSubdivision = useDiamondSubdivision;}
+
 	virtual int	getShapeType() const
 	{
 		return TERRAIN_SHAPE_PROXYTYPE;