[PATCH] Add a5/3 support.

Hello.

Attached patch will bring a5/3 support to osmo_a5. The implementatin is done based on spec, results are compared to reference implementation from standard and test vectors.

Unfortunately there are several deficiencies: - it doesn't work with real phonein test network yet - no tests included - code is probably suboptimal here and there

Anyway I would love to read your comments. It would be especially great if someone will manage to test it against real phones in actual network.