libcommon: join gsm_data_shared.* into gsm_data.*

The separation of gsm_data_shared.* from gsm_data.* historically allowed
compiling parts of it into osmo-bts, which we have dropped since (osmo-bts has
its own copy now). Even though gsm_data.* now becomes rather large by it,
remove the legacy separation to get rid of the "shared" naming, which is no
longer meaningful. A future patch might separate into meaningful smaller bits,
if we get the time.

Change-Id: Ie247bc492efb331871d970c56700595ad3f7e201
10 files changed