gb: Add beginnings of a new BSSGP implementation

Similar to ns2 superseding ns, we now also intoduce a next generation
of BSSGP related code to libosmogb.  However, this is not aiming to
be a full implementation yet, but simply those parts that we currently
need from the revamped osmo-gbproxy.

The gprs_bssgp2.[ch] differs in two ways from the old code:
* it separates message encoding from message transmission
* it supports more recent specs / IEs

bssgp_bvc_fsm.c is a genric implementation of the BSSGP BVC
RESET/BLOCK/UNBLOCK logic with support for both PTP and signaling,
both on the SGSN side and the BSS side.

Change-Id: Icbe8e4f03b68fd73b8eae95f6f6cccd4fa9af95a
diff --git a/src/gb/Makefile.am b/src/gb/Makefile.am
index b140727..ea1cfde 100644
--- a/src/gb/Makefile.am
+++ b/src/gb/Makefile.am
@@ -26,6 +26,7 @@
 		  gprs_bssgp_bss.c \
 		  gprs_ns2.c gprs_ns2_udp.c gprs_ns2_frgre.c gprs_ns2_fr.c gprs_ns2_vc_fsm.c gprs_ns2_sns.c \
 		  gprs_ns2_message.c gprs_ns2_vty.c \
+		  gprs_bssgp2.c bssgp_bvc_fsm.c \
 		  common_vty.c frame_relay.c
 endif