i386 do not support i386

[Rostislav Krasny]

> FreeBSD 6.0R don't support 386 processors according to the release
> notes, maybe it's time to change the name of the i386 platform to the
> x86 platform.

16-bit 8086, 8088, 80186 and 80286 are x86 processors too. 80386 was
the first 32-bit processor from Intel, and it had many other
significant architectural changes. I believe the i386 architecture
name is righteous for 80386 successors, even without the 80386
particular support. That's just my IMHO.