Create skeleton for libosmo-gprs-gmm

The library itself only contains a bunch of boilerplate to build the
library and have usual initialization, logging, prim APIs.
There's not yet much logic specific in it yet, but will make next
commits easier to review.

Related: OS#5501
Change-Id: Ie098576954a55e5046c2463390ab7133511c1eb3
---
M Makefile.am
M configure.ac
M contrib/libosmo-gprs.spec.in
M debian/control
A debian/libosmo-gprs-gmm-dev.install
A debian/libosmo-gprs-gmm0.install
M include/osmocom/gprs/Makefile.am
A include/osmocom/gprs/gmm/Makefile.am
A include/osmocom/gprs/gmm/gmm.h
A include/osmocom/gprs/gmm/gmm_prim.h
A include/osmocom/gprs/gmm/gmm_private.h
A libosmo-gprs-gmm.pc.in
M src/Makefile.am
A src/gmm/Makefile.am
A src/gmm/gmm.c
A src/gmm/gmm_prim.c
A src/gmm/misc.c
M tests/Makefile.am
A tests/gmm/Makefile.am
A tests/gmm/gmm_prim_test.c
A tests/gmm/gmm_prim_test.err
A tests/gmm/gmm_prim_test.ok
M tests/testsuite.at
23 files changed, 851 insertions(+), 0 deletions(-)