second draft: add Bitfields to D

[Walter Bright]

On 5/3/2024 5:52 AM, Patrick Schluter wrote:
> Not true. x86 provides BMI1 instructions which are present in x86 CPUs at least 
> since 2013.
> ARM also provides bit field instructions and quite a number of legacy CPU's also 
> had bitfield instructions (m68k, NEC V30, Itanium, PowerPC, etc.).
> Doesn't change the issues with language bitfields

I'd be very surprised if it didn't work by reading the entire field first.

https://www.felixcloutier.com/x86/bextr