CPUTYPE?=athlon-xp breaks loader (was Re: instant reboot when trying to load recent RELENG_5 kernel)

[Jon Noack]

On up-to-date RELENG_5_3, compiling the loader with CPUTYPE?=athlon-xp
results in an instant reboot when the loader attempts to load a kernel. 
As the loader will preload the default kernel before presenting the boot
prompt, there is a reboot before you even get to the boot prompt...  The
end result is an unworkable install.  I do not see this issue on my
Pentium III and Pentium IV systems (using "p3" and "p4" for CPUTYPE,
respectively), although there is a similar problem reported on a Pentium M
(have not verified CPUTYPE is being used, however).

I first noticed this issue on October 15th.  My previous build on October
12th worked fine.  At the time I was tracking RELENG_5, but prior to that
I was tracking HEAD.

If other folks with Athlon XPs (or Pentium Ms) could give this a shot that
would be great.  It would be good to know if it's a real problem or just
my system.

Thanks,
Jon