Revamped concurrency API

[Andrei Alexandrescu]

Jeremie Pelletier wrote:
> Jeremie Pelletier wrote:
>> I agree here, while I think Andrei's book is a must for the community 
>> to grow, it should rush the compiler. I strongly believe D2 needs 
>> proper shared and lent semantics, or else we're just creating a 
>> stepping stone for D3, leaving D2 in a state that isn't suited for 
>> concurrent model implementations in a type-safe manner.
> 
> s/should rush/shouldn't rush/

For the record, I delayed signing for the book for quite a few months. 
Before I did sign, there was solemn agreement in the D team that we can 
commit. The book is already late by a few months. If the book is trying 
to rush anything, it's doing a lousy job at that.

Andrei