Add support for printing IPSEC protocol stats if the kernel was compiled

Add support for printing IPSEC protocol stats if the kernel was compiled
with FAST_IPSEC rather than the KAME IPSEC stack.

Note that the output of "netstat -s -p ipsec" differs depending on which
stack is compiled into the kernel since they each keep different stats.
This delta also adds the "esp", "ah", and "ipcomp" protocol stats, which
are also available when the kernel is compiled with the FAST_IPSEC stack
(e.g. "netstat -s -p esp").

Submitted by:	Matt Titus <titus at nttmcl dot com>
MFC after:	3 days