second draft: add Bitfields to D

[Walter Bright]

On 4/30/2024 1:48 PM, Timon Gehr wrote:
> Well, I am bringing it up because the DIP draft ignores type qualifiers so far 
> (and explicitly only lists unqualified types for support). What is happening 
> with `shared` I think has not been fully pinned down, but last I heard the goal 
> was to get implicit atomics.

Since a bitfield can be part of a shared object, of course the shared type 
should exist for it. But since you cannot take a reference to a bitfield, you're 
going to have to dip into @system code to manipulate it, and it's up to the 
programmer to figure out what to do.

Immutable means read only. I don't see any issue with that, either.