Further tweaked restitution for track and bowling ball to avoid

bowling balls jumping up and down, while still maintaining a push
back for soccer balls.

src/items/bowling.cpp

@@ -57,7 +57,7 @@ Bowling::Bowling(AbstractKart *kart)
 
     createPhysics(y_offset, btVector3(0.0f, 0.0f, m_speed*2),
                   new btSphereShape(0.5f*m_extend.getY()),
-                  1.0f /*restitution*/,
+                  0.8f /*restitution*/,
                   -70.0f /*gravity*/,
                   true /*rotates*/);
     // Even if the ball is fired backwards, m_speed must be positive,

src/physics/triangle_mesh.cpp

@@ -188,7 +188,7 @@ void TriangleMesh::createPhysicalBody(btCollisionObject::CollisionFlags flags,
     m_motion_state = new btDefaultMotionState(startTransform);
     btRigidBody::btRigidBodyConstructionInfo info(0.0f, m_motion_state,
                                                   m_collision_shape);
-    info.m_restitution = 1.0f;
+    info.m_restitution = 0.8f;
     m_body=new btRigidBody(info);
     World::getWorld()->getPhysics()->addBody(m_body);