Make raycast benchmark default, to show improved raycasting performance.

Add rayTest to btBroadphaseInterface, and implement efficient version for btDbvtBroadphase to accelerate raycasting.
btAxisSweep3, btSimpleBroadphase and btMultiSapBroadphase implement brute-force method (as before). For now, it is recommended to use btDbvtBroadphase for fastest world raycast.

src/BulletCollision/BroadphaseCollision/btSimpleBroadphase.cpp

@@ -151,7 +151,14 @@ void	btSimpleBroadphase::setAabb(btBroadphaseProxy* proxy,const btVector3& aabbM
 	sbp->m_aabbMax = aabbMax;
 }
 
-
+void	btSimpleBroadphase::rayTest(const btVector3& rayFrom,const btVector3& rayTo, btBroadphaseRayCallback& rayCallback)
+{
+	for (int i=0;i<m_numHandles;i++)
+	{
+		btSimpleBroadphaseProxy* proxy = &m_pHandles[i];
+		rayCallback.process(proxy);
+	}
+}