sgsn: Add gprs_subscriber.c

This patch adds GPRS specific functions for gsm_subscriber objects
(allocation, retrieval, deletion) and subscriber data
requests/updates. The sgsn_update_subscriber_data callback is used to
notify the sgsn about updates and is extended by a parameter that
passes a reference to a gsm_subscriber.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/tests/sgsn/Makefile.am b/openbsc/tests/sgsn/Makefile.am
index f822aac..0e5d009 100644
--- a/openbsc/tests/sgsn/Makefile.am
+++ b/openbsc/tests/sgsn/Makefile.am
@@ -6,6 +6,9 @@
 noinst_PROGRAMS = sgsn_test
 
 sgsn_test_SOURCES = sgsn_test.c
+sgsn_test_LDFLAGS = \
+	-Wl,--wrap=sgsn_update_subscriber_data
+
 sgsn_test_LDADD = \
 	$(top_builddir)/src/gprs/gprs_llc_parse.o \
 	$(top_builddir)/src/gprs/gprs_llc.o \
@@ -16,6 +19,8 @@
 	$(top_builddir)/src/gprs/sgsn_vty.o \
 	$(top_builddir)/src/gprs/sgsn_libgtp.o \
 	$(top_builddir)/src/gprs/sgsn_auth.o \
+	$(top_builddir)/src/gprs/gprs_subscriber.o \
+	$(top_builddir)/src/libcommon/libcommon.a \
 	$(LIBOSMOCORE_LIBS) \
 	$(LIBOSMOGSM_LIBS) \
 	$(LIBOSMOGB_LIBS) \