Begin migrating net80211 code from ifconfig into lib80211.

[adrian]

Summary

This is a very simple first pass at extracting the net80211 interface
code out of ifconfig and into a library so other tools can be written
without having to use the ioctl API directly.

It's mostly just the regulatory domain and basic ioctl access.
I'll add more of the code from ifconfig in at a later stage.

[adrian]

add ifconfig