add Bullet 2.x constraint solver tests for hinge, with large mass ratio

experiment with Midi controls in PairBenchmark to tune variables (will move it into a utility class, so every demo can easier use it in the future)
fix issue with broadphase, not initializing all pairs properly at pair array overflow

Demos3/bullet2/BasicDemo/BasicDemo.h

@@ -21,10 +21,10 @@ public:
 	
 	void	createGround(int cubeShapeId);
 
-	void	initPhysics();
-	void	exitPhysics();
-	void	renderScene();
-	void	stepSimulation(float dt);
+	virtual void	initPhysics();
+	virtual void	exitPhysics();
+	virtual void	renderScene();
+	virtual void	stepSimulation(float dt);
 };