sync with KAME.
sync with KAME.

check if the CPU supports TSC in i386 to avoid panic
on non-pentium CPUs.
use pentium_mhz or alpha's cycles_per_usec.

add a protection against a bogus IP header length
when parsing the header.
be more careful about mbuf data length.
a backtrace reported by
"Robert John Shepherd" <robert@reviewer.co.uk>

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars