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/configure.ac b/configure.ac
index be66d51..03acc0c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -44,6 +44,7 @@
 PKG_CHECK_MODULES(LIBOSMOSIGTRAN, libosmo-sigtran >= 0.9.0)
 PKG_CHECK_MODULES(LIBOSMOSCCP, libosmo-sccp >= 0.9.0)
 PKG_CHECK_MODULES(LIBOSMOMGCPCLIENT, libosmo-mgcp-client >= 1.3.0)
+PKG_CHECK_MODULES(LIBOSMOGSUPCLIENT, libosmo-gsup-client >= 0.2.1)
 
 AC_ARG_ENABLE(sanitize,
 	[AS_HELP_STRING(
@@ -193,7 +194,6 @@
     src/Makefile
     src/libmsc/Makefile
     src/libvlr/Makefile
-    src/libgsupclient/Makefile
     src/osmo-msc/Makefile
     src/utils/Makefile
     tests/Makefile