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/debian/control b/debian/control
index 6219ea4..e607d10 100644
--- a/debian/control
+++ b/debian/control
@@ -18,6 +18,7 @@
                libosmo-sigtran-dev (>= 0.8.0),
                libosmo-abis-dev,
                libosmo-mgcp-client-dev (>= 1.1.0),
+               libosmo-gsup-client-dev (>= 0.2.1),
                libosmo-netif-dev (>= 0.1.0),
                libosmo-ranap-dev (>= 0.2.0)
 Standards-Version: 3.9.8