Encryption branch

Dear Sylvaion,

I've tried my best to forward-port your 'sylvain/encryption' branch to current OpenBSC, and you can find the result in laforge/encryption.

I haven't yet had time to test it, but I wouldn't be surprised to see something break, considering that your code predated the introduction of 'gsm_subscriber_connection'.

Unfortunately merging the branch to master is also not really an option right now, as it is likely to cause trouble with the BSC/MSC split, as we will have to align our encryption support with how the A-Interface between BSC and MSC handles things.

Nonetheless, I really would like to see this feature move ahead. There is definitely a demand for it in the research community.

Regards, Harald