sys: Add a deprecation warning for 32-bit kernels.

[jhb]

Summary

Per recent discussions on arch@ and at the BSDCan developer summit, we
are considering removing support for 32-bit platforms (in some form)
for 15.0 (at the earliest). A final decision on what will ship in
15.0 will be made closer to the release of 15.0. However, we should
communicate the potential deprecation in 14.0 to provide notice to
users.

[emaste]

sys/kern/init_main.c

400

"FreeBSD 15.0"?

[brooks]

It might be wise to expand the commit message with a bit more explanation of what's going on.

[jhb]

I'm also posting this series to arch@ again as a follow-up, but yes, more detail in the commit log is probably warranted.

[imp]

I agree with Ed: I think we normally say FreeBSD X in our messages instead of just X

[jhb]

Add FreeBSD

[jhb]

I'm also posting this series to arch@ again as a follow-up, but yes, more detail in the commit log is probably warranted.