src: Add old state as argument to CallsCall's state-changed signal

src/calls-ofono-call.c

@@ -87,9 +87,18 @@ static void
 change_state (CallsOfonoCall *self,
               CallsCallState  state)
 {
+  CallsCallState old_state = self->state;
+
+  if (old_state == state)
+    {
+      return;
+    }
+
   self->state = state;
   g_signal_emit_by_name (CALLS_CALL (self),
-                         "state-changed", state);
+                         "state-changed",
+                         state,
+                         old_state);
 }