gprs: Add GSUP client

This commit adds the client code to get subscriber information from a
remote server. It provides an IPA over TCP connection to transmit and
receive GSUP messages.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/gprs/Makefile.am b/openbsc/src/gprs/Makefile.am
index d45aaee..b5a61b1 100644
--- a/openbsc/src/gprs/Makefile.am
+++ b/openbsc/src/gprs/Makefile.am
@@ -23,7 +23,7 @@
 			sgsn_main.c sgsn_vty.c sgsn_libgtp.c \
 			gprs_llc.c gprs_llc_parse.c gprs_llc_vty.c crc24.c \
 			sgsn_ctrl.c sgsn_auth.c gprs_subscriber.c \
-			gprs_gsup_messages.c gprs_utils.c
+			gprs_gsup_messages.c gprs_utils.c gprs_gsup_client.c
 osmo_sgsn_LDADD = 	\
 			$(top_builddir)/src/libcommon/libcommon.a \
 			-lgtp $(OSMO_LIBS) $(LIBOSMOABIS_LIBS)