split libgb into a separate library for outside use

This also removes the dependency to osmo_sock() inside libcommon and
replaces it with osmo_sock_* from libosmocore
diff --git a/openbsc/src/libgb/gprs_bssgp_vty.c b/openbsc/src/libgb/gprs_bssgp_vty.c
index a0d74ac..256e8af 100644
--- a/openbsc/src/libgb/gprs_bssgp_vty.c
+++ b/openbsc/src/libgb/gprs_bssgp_vty.c
@@ -26,17 +26,13 @@
 
 #include <arpa/inet.h>
 
-#include <openbsc/gsm_data.h>
 #include <osmocom/core/msgb.h>
 #include <osmocom/gsm/tlv.h>
 #include <osmocom/core/talloc.h>
 #include <osmocom/core/select.h>
 #include <osmocom/core/rate_ctr.h>
-#include <openbsc/debug.h>
-#include <openbsc/signal.h>
-#include <openbsc/gprs_ns.h>
-#include <openbsc/gprs_bssgp.h>
-#include <openbsc/vty.h>
+#include <osmocom/gprs/gprs_ns.h>
+#include <osmocom/gprs/gprs_bssgp.h>
 
 #include <osmocom/vty/vty.h>
 #include <osmocom/vty/command.h>
@@ -44,6 +40,11 @@
 #include <osmocom/vty/telnet_interface.h>
 #include <osmocom/vty/misc.h>
 
+#include <openbsc/vty.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/debug.h>
+
+
 /* FIXME: this should go to some common file as it is copied
  * in vty_interface.c of the BSC */
 static const struct value_string gprs_bssgp_timer_strs[] = {