[lwip-users] lwIP Windows implementation

[box]

I've ported lwIP on Windows in userspace as a cool way to work around 
Windows TCP/IP stack limitation. See here: http://www.dupuis.me/node/21

The stack performs quite well even in user space how ever:
- the stack tend to create a lot of semaphore for simulating blocking 
call
- it would be nice to have no blocking function or callback for 
netcomm_* API

Laurent