Proposal for dual memory management

[F. Almeida]

== Quote from Petr Janda (janda.petr at gmail.com)'s article
> I think what has to be done is clearly indicate which features of D can't be used
> when managing your own memory. Best if compiler could warn us.

Aside from manual allocation and deallocation, there should be very little difference between what you can do
to managed and to unmanaged objects.

We could eventually adopt a @unsafe attribute that tells the compiler to disable whatever is unsafe code
whenever using the SafeD subset. This would make manually managed code refuse to compile. But I don't think
this step should be taken before the GC is updated and optimized.