Log Message:
zabbix: rewrite to use sysctl(), code lifted from netstat/if.c.

This rewrites src/libs/zbxsysinfo/netbsd/net.c's to not do
"kmem groveling" but instead use the more modern sysctl()
method which is now the preferred method to get network stats.

This fixes the build on netbsd-10, and has been built and tested
on 8.2, and build-verified on 9.3.

OK'ed by gdt@

Bump PKGREVISION.