Update the testbed to use PhysicsHooks.

examples2d/all_examples2.rs

@@ -18,6 +18,7 @@ mod debug_box_ball2;
 mod heightfield2;
 mod joints2;
 mod locked_rotations2;
+mod one_way_platforms2;
 mod platform2;
 mod polyline2;
 mod pyramid2;
@@ -65,6 +66,7 @@ pub fn main() {
         ("Heightfield", heightfield2::init_world),
         ("Joints", joints2::init_world),
         ("Locked rotations", locked_rotations2::init_world),
+        ("One-way platforms", one_way_platforms2::init_world),
         ("Platform", platform2::init_world),
         ("Polyline", polyline2::init_world),
         ("Pyramid", pyramid2::init_world),