DIP77 - Fix unsafe RC pass by 'ref'

[Martin Nowak via Digitalmars-d]

On Thursday, 9 April 2015 at 12:05:16 UTC, Michel Fortin wrote:
> """
> An object is assumed to be reference counted if it has a 
> postblit and a destructor, and does not have an opAssign marked 
> @system.
> """

It seems to only fit to RCO, I'm not positive though.
We should formalize this, by documenting it and by adding isRCO 
traits to phobos.