[cpp-threads] Asynchronous Function Proposal

[Peter Dimov]

> Extending the lifetime of a function argument after the function returns 
> relies on this property, and this is an issue that is conceptually 
> orthogonal to thread locals.
>
> void f( T & t1, T t2 )
> {
>    t1 = t2;
> }
>
> This extends the lifetime of t2 to that of the object t1 refers to.

Incidentally, scoped allocators are not a problem (even with thread locals). 
The assignment doesn't change t1's allocator.