Implementation of passive scanning at LL 

Hello,

I just extended the LL functionality by adding an implementation of passive scanning. 

Please tell me if I didn't respected some of yours coding conventions or if you want me to apply changes ?

I plan to add more functionality very soon, my objective is to implement a master device (central role) with precise requirements on timing and number of devices. I don't need the full stack with GAP/GATT functions so I will focus on simplified operation at relatively low level.

Nordic S120 soft device is limited to 8 simultaneous connections and won't allow me to make address filtering in software so, let's go Open Source !

Muito obrigado pelo trabalho que vocês ja fizeram :)

Tom