add ADDR_ADD and ADDR_DEL devctl event for IFNET

[rozhuk.im-gmail.com]

Summary

Add devd event on network iface address add/remove.
Can be used to automate actions on any address change.

Test Plan

Apply patch, rebuild and reinstall kernel.

Run in terminal1:
cat /var/run/devd.pipe

In terminal2:
ifconfig lan0 alias 192.168.1.1/24
ifconfig lan0 -alias 192.168.1.1
ifconfig lan0 inet6 1111::

Result
terminal1 will produce output:
!system=IFNET subsystem=lan0 type=ADDR_ADD address=192.168.1.1
!system=IFNET subsystem=lan0 type=ADDR_DEL address=192.168.1.1
!system=IFNET subsystem=lan0 type=ADDR_ADD address=1111::

*lan0 must me replaced with real network interface name.

[imp]

can you add the ADDR_ADD and ADDR_DEL to the table in sbin/devd/devd.conf.5 please?

[rozhuk.im-gmail.com]

Update sbin/devd/devd.conf.5

[rozhuk.im-gmail.com]

Add "#if defined(INET) || defined(INET6)" for vars.

[imp]

looks good to me...

[imp]

Note: minor style tweaks I've noted here I've just done when landing.

sys/net/route.c

714

A blank line is needed before inet_ntoa_r.
Also, that can be on one line
Also, there's at least one extra set of parens here.

725

a blank line is needed between the strbuf and ip6_sprintf lines.