This introduces:
* a basic wtap interface
* a HAL, which implements an abstraction layer for implementing
different device behavious;
* A visibility plugin, which allows for control over which nodes
see other nodes (useful for mesh work.)
It doesn't yet implement sta/adhoc/hostap modes but these are quite
feasible to implement.
Monthadar uses it to do 802.11s mesh verification.
The userland tools will be committed in a follow-up commit.
Submitted by: Monthadar Al Jaberi <monthadar@gmail.com>
