[D-runtime] Mixing GC and non-GC in D. (AKA, "don't touch GC-references from DTOR, preferably don't use DTOR at all")

[Ulrik Mikaelsson]

> Either way, here's an alternate suggestion: add the objects in unmanaged
> memory to the list of GC roots. If you use a bulk allocator, you can make
> the allocator add the whole pool.
FYI: I don't have access to build-env for D2/druntime, but I've
created an implementation for Tango, in
http://www.dsource.org/projects/tango/ticket/2024. It might be of
interest to port to druntime, with the mentioned D2-improvements to
SmartRef.