mac80211 802.11s networking code

This is a cleaned up version of Luis's 11s code which doesn't break
git bisect, compiles cleanly and ultimately has a lot less #ifdefs.

Let's merge this code and fix the remaining problems later.

Notably, this marks 11s as BROKEN because of endianness problems in it.

John, this applies after the following patches:
 * mac80211: fix IBSS code
 * mac80211: rework TX filtered frame code
 * mac80211: atomically check whether STA exists already
 * mac80211: fix debugfs_sta print_mac() warning
 * mac80211: Disallow concurrent IBSS/STA mode interfaces

Please apply those first and then this set, I will respin my sta_info
rework on top of these patches (it needs bugfixes anyway.)

johannes