[gprs] Build the SGSN stand-alone and not as part of bsc_hack

Instead of continuing to add more and more functionality to the
bsc_hack binary, we should have the new SGSN code run as a separate
executable.

After this commit we now build a 'osmo_sgsn' executable, using its
own osmo_sgsn.cfg config file.

However, the SGSN is not yet functional, mainly due to the fact that
the BSSGP and GMM code are written with the assumption that there
is a msgb->trx->bts and the according 'sturct gsm_bts' data model
around - which clearly is no longer the case outside of bsc_hack.
10 files changed
tree: 3eb26d769377da53a50c2a9d871580e73451427e
  1. hlrsync/
  2. libosmocore/
  3. linux-kernel/
  4. openbsc/
  5. rrlp-ephemeris/
  6. wireshark/