bug#63072: 28.2; CC Mode: Fix "bsd" style and add "freebsd" and "openbsd" ones

[Olivier Certner <ocert.dev@free.fr>]

> If the styles don't change in practice, then I'm okay with adding
> them.  But then I wonder why you bothered to mention the fact that
> they do change.

I thought this was clear, but apparently not. I mentioned the possibility of a 
change, yes, because you and I care about backwards compatibility. To quote 
you: "I don't think we can change a style that was in use for such a long 
time".

There may be changes in the project styles, maybe next month, maybe in ten 
years, maybe in twenty. I do not think the probability is 0 over such a long 
period of time. What I would not want is you or someone else telling me in 10 
or 20 years, after such a change: "I don't think we can change a style that 
was in use for such a long time". What I want instead is that, e.g., "freebsd" 
can be changed as necessary. I specifically do not want to then be told to 
create another style named "freebsd2" or whatever. For that to be possible, 
users must be warned that these styles, although almost always stable, are 
not, and will not, be set in stone for eternity, contrary to, perhaps, "bsd" 
or "whitesmith". And I even offered a scheme with additional styles that will 
never change, if you think that is useful (I think it might be and is so cheap 
to implement that I think we should do it anyway, even if in the end nobody 
uses it).

Is that clear now?

-- 
Olivier Certner