Remove local libgsupclient; Use libosmo-gsup-client from osmo-hlr

osmo-hlr has recently (as of Change-Id
Iad227bb477d64da30dd6bfbbe1bd0c0a55be9474) a working shared library
implementation of libosmo-gsup-client.

We can remove the local implementation in osmo-sgsn and use the
system-installed shared library instead.

Change-Id: I6f542945403cf2e3ddac419186b09ec0e2d43b69
diff --git a/src/gprs/Makefile.am b/src/gprs/Makefile.am
index 0f7c5fa..ba5dfd6 100644
--- a/src/gprs/Makefile.am
+++ b/src/gprs/Makefile.am
@@ -13,6 +13,7 @@
 	$(LIBOSMOCTRL_CFLAGS) \
 	$(LIBOSMOABIS_CFLAGS) \
 	$(LIBOSMOGB_CFLAGS) \
+	$(LIBOSMOGSUPCLIENT_CFLAGS) \
 	$(COVERAGE_CFLAGS) \
 	$(LIBCARES_CFLAGS) \
 	$(LIBGTP_CFLAGS) \
@@ -84,11 +85,11 @@
 	slhc.c \
 	gprs_llc_xid.c \
 	v42bis.c \
-	gsup_client.c \
 	$(NULL)
 osmo_sgsn_LDADD = \
 	$(OSMO_LIBS) \
 	$(LIBOSMOABIS_LIBS) \
+	$(LIBOSMOGSUPCLIENT_LIBS) \
 	$(LIBCARES_LIBS) \
 	$(LIBGTP_LIBS) \
 	-lrt \