std.typecons.Rebindable not usable with vibe.core.concurrency.receive

[atilaneves]

The template that checks for weakly isolated arguments doesn't take Rebindable into account. Given that immutable classes don't work with receive from the stdlib, Rebindable is the only way that works there and it doesn't work with vibe.d, making shared classes the only way to send class references to another task.