Pull up following revision(s) (requested by maxv in ticket #230):
sys/arch/i386/conf/GENERIC: revision 1.1158
Disable vm86 by default. The use case is limited, and the potential for
damage is too high.
This code is fragile, and relies on a certain number of assumptions, some
of which are not be totally true. For example, it relies on the fact that
a 16bit process cannot perform a syscall, but verily it can. The slighest
confusion in the trap frame can lead to ring0 exploits. Also, I'm not
convinced that it interacts well with the compatibility layers.

(snj)