destructor, postblit constructor --- force calling always

[Carl Sturtivant]

> D's structs don't have identity. That means, they can be moved 
> without notice at any point in the program. AFAIK the compiler 
> even does that when handling exceptions in a few cases (e.g. 
> with structs on the stack). Having moveable value types allows 
> for a lot of optimizations, both on the compiler side as well 
> as when implementing e.g. containers in user code. So no there 
> is no way to always get notified. I also proposed a move 
> constructor in the past, but the idea was not well recieved. 
> When I needed a move constructor, usually adding another level 
> of indirection solved the problem.

Thanks for that discussion. As you might have guessed, adding 
another level of indirection is what I was trying to avoid. A 
move constructor would have taken care of my problem.

What about destructors, are they always called, or is this 
another optimization if the struct is in it's default .init state?