Implement multibody joints and the new solver

examples2d/locked_rotations2.rs

@@ -10,7 +10,8 @@ pub fn init_world(testbed: &mut Testbed) {
      */
     let mut bodies = RigidBodySet::new();
     let mut colliders = ColliderSet::new();
-    let joints = JointSet::new();
+    let impulse_joints = ImpulseJointSet::new();
+    let multibody_joints = MultibodyJointSet::new();
 
     /*
      * The ground
@@ -51,6 +52,6 @@ pub fn init_world(testbed: &mut Testbed) {
     /*
      * Set up the testbed.
      */
-    testbed.set_world(bodies, colliders, joints);
+    testbed.set_world(bodies, colliders, impulse_joints, multibody_joints);
     testbed.look_at(point![0.0, 0.0], 40.0);
 }