update README with obsolescence information

README.md

@@ -1,8 +1,10 @@
-============
-chan_openbsc
-============
+# chan_openbsc
 
-Channel driver for the OpenBSC project ( http://openbsc.gnumonks.org/ )
+Pre-historic Channel driver for the [OpenBSC](https://osmocom.org/projects/openbsc) project
+
+**THIS CODE IS LONG OBSOLETE AND FOR HISTORIC REFERENCE ONLY**
+
+Please use [osmo-sip-connector](https://osmocom.org/projects/osmo-sip-conector/wiki) instead.
 
 
 Building