On heap segregation, GC optimization and @nogc relaxing

[Dicebot via Digitalmars-d]

Finally got a look at your proposal. While I do agree with many 
initial statements and, specifically, proposal for heap 
segregation, proposed semantics of `owned` does leave me 
skeptical. It is effectively a more refined/mature approach to 
"cooking of immutables" concept and Marc proposal, while being 
more complicated semantic-wise, allows for much more than that.