layer23: Complete rework of MCC and MNC structure.

layer23: Complete rework of MCC and MNC structure.

Instead of handling numerical MCC and MNC, they are now stored and handled
hexadecimal, like they are received by the network. This makes it possible
to correctly handle 2 and 3 digits MNC. Internally 2 digit MNCs are stored
as 0xXXf, and 3 digits MNC are stored as 0xXXX, where X is the digit 0..9.

The length of MNC in the IMSI (2 or 3 digits) depend on the MNC length
trying to match. Anyway that MNC name can be printed even without knowing the
actual length. This is done by matching the IMSI against list of networks.

PLEASE REMOVE "/etc/osmocom/*.ba", because the MCC and MNC stored there is
not valid anymore.