cfg80211: managed mode wext compatibility

This adds code to make it possible to use the cfg80211
connect() API with wireless extensions, and because the
previous patch added emulation of that API with auth()
and assoc(), by extension also supports wext on that.
At the same time, removes code from mac80211 for wext,
but doesn't yet clean up mac80211's mlme code more.

Signed-off-by: Samuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>