Testbed physx backend: re-add joints.

examples3d/all_examples3.rs

@@ -31,7 +31,6 @@ mod platform3;
 mod primitives3;
 mod restitution3;
 mod sensor3;
-mod stacks3;
 mod trimesh3;
 
 fn demo_name_from_command_line() -> Option<String> {
@@ -82,7 +81,6 @@ pub fn main() {
         ("Locked rotations", locked_rotations3::init_world),
         ("Platform", platform3::init_world),
         ("Restitution", restitution3::init_world),
-        ("Stacks", stacks3::init_world),
         ("Sensor", sensor3::init_world),
         ("TriMesh", trimesh3::init_world),
         ("Keva tower", keva3::init_world),