since parent collision is always disabled by default for self-collision, we add a new flag

URDF_USE_SELF_COLLISION_INCLUDE_PARENT, to force self-collision between direct parent/child (not recommended in general)

examples/Importers/ImportURDFDemo/URDF2Bullet.h

@@ -31,6 +31,7 @@ enum ConvertURDFFlags {
   CUF_ENABLE_CACHED_GRAPHICS_SHAPES = 1024,
   CUF_ENABLE_SLEEPING=2048,
   CUF_INITIALIZE_SAT_FEATURES=4096,
+  CUF_USE_SELF_COLLISION_INCLUDE_PARENT = 8192,
 };
 
 struct UrdfVisualShapeCache