Interface C++ objects with `wasMoved`?

[sls1005]

As I can remember, calling `wasMoved` without calling `=destroy` first will 
cause memory leak. I guess it nil-ifies the reference without freeing the 
memory, as it's intend to be used on an object that's already destroyed, 
preventing it from being destroyed twice. I also make use of this for 
initializing GC'ed variables that's never initialized to zero.