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-msc and use the
system-installed shared library instead.

Change-Id: I6f542945403cf2e3ddac419186b09ec0e2d43b69
diff --git a/src/libmsc/Makefile.am b/src/libmsc/Makefile.am
index a2560ea..90bbbf8 100644
--- a/src/libmsc/Makefile.am
+++ b/src/libmsc/Makefile.am
@@ -15,6 +15,7 @@
 	$(LIBOSMOSIGTRAN_CFLAGS) \
 	$(LIBOSMOSCCP_CFLAGS) \
 	$(LIBOSMOMGCPCLIENT_CFLAGS) \
+	$(LIBOSMOGSUPCLIENT_CFLAGS) \
 	$(LIBOSMORANAP_CFLAGS) \
 	$(NULL)