Release D 2.089.0

[John Chapman]

On Tuesday, 5 November 2019 at 19:05:10 UTC, Manu wrote:
> Incidentally, in your sample above there, `a` and `b` are not 
> shared... why not just write: `cas(&a, null, b);` ?? If source 
> data is not shared, you shouldn't cast to shared.

Because casts were needed in 2.088 and earlier and I just updated 
to 2.089, unaware of the API change. Should I log `null` not 
working as a bug?