implement support for 3-digit MNC with leading zeros

Add 3-digit flags and use the new RAI and LAI API from libosmocore throughout
the code base to be able to handle an MNC < 100 that has three digits (leading
zeros).

Note that in gbproxy_test.ok, 0-0 changes to 000-000 instead of 000-00, because
the parsed ra buffer is 000000 which results in 000-000, while 00f000 would
result in 000-00. IOW this is expected.

Change-Id: I7437dfaa586689e2bef0d4be6537e5577a8f6c26
11 files changed