[dmd-concurrency] Defining shared delegates

[Andrei Alexandrescu]

One suggestion about shared delegates: should we take the executive 
decision to not define them at all? There's nothing you can do with 
delegates that you can't do with classes. Although generally delegates 
do justify their existence because they're more comfy than e.g. local 
classes, it doesn't strike me as obvious we'll need comparable 
convenience when dealing with shared classes.

Andrei