Adding more OpenBSC object files to Makefile.am

This is required, so it works in my environment. Might be revised soon.
diff --git a/src/Makefile.am b/src/Makefile.am
index 004da4b..1728c9e 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -23,7 +23,7 @@
 OPENGGSN_DIR = $(top_srcdir)/../openggsn
 
 AM_CPPFLAGS = $(STD_DEFINES_AND_INCLUDES) -I$(OPENBSC_DIR)/include
-AM_CXXFLAGS = -Wall -ldl -pthread
+AM_CXXFLAGS = -Wall -ldl -pthread -lgtp
 
 noinst_LTLIBRARIES = libgprs.la
 
@@ -65,6 +65,13 @@
 	$(OPENBSC_DIR)/src/libgb/gprs_bssgp_bss.o \
 	$(OPENBSC_DIR)/src/libgb/gprs_bssgp_util.o \
 	$(OPENBSC_DIR)/src/libgb/gprs_ns_frgre.o \
+	$(OPENBSC_DIR)/src/libcommon/socket.o \
+	$(OPENBSC_DIR)/src/gprs/gprs_llc.o \
+	$(OPENBSC_DIR)/src/gprs/gprs_gmm.o \
+	$(OPENBSC_DIR)/src/gprs/gprs_sgsn.o \
+	$(OPENBSC_DIR)/src/gprs/sgsn_libgtp.o \
+	$(OPENBSC_DIR)/src/gprs/gprs_sndcp.o \
+	$(OPENBSC_DIR)/src/gprs/crc24.o \
 	$(LIBOSMOCORE_LIBS) \
 	$(LIBOSMOGSM_LIBS) \
 	$(COMMON_LA)