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/HingeDemo.h

@@ -0,0 +1,28 @@
+
+#ifndef HINGE_DEMO_H
+#define HINGE_DEMO_H
+
+#include "BasicDemo.h"
+
+class HingeDemo : public BasicDemo
+{
+public:
+	static BulletDemoInterface* MyCreateFunc(SimpleOpenGL3App* app)
+	{
+		return new HingeDemo(app);
+	}
+
+	HingeDemo(SimpleOpenGL3App* app);
+
+	class btMultiBody* createFeatherstoneHinge(class btMultiBodyDynamicsWorld* world, const struct btMultiBodySettings2& settings);
+
+
+	virtual void	initPhysics();
+	virtual void	exitPhysics();
+
+	virtual void	renderScene();
+
+};
+
+#endif //HINGE_DEMO_H
+