[#3218] we must lock the glib mainloop using the gdk_thread_enter/leave

	in main and in each threads

sflphone-client-gnome/src/callable_obj.c

@@ -139,6 +139,8 @@ void *threaded_clock_incrementer(void *pc) {
     int duration;
     time_t start, current;
 
+    gdk_threads_enter ();
+
     set_timestamp(&(call->_time_current));
 
     start = call->_time_start;
@@ -171,6 +173,8 @@ void *threaded_clock_incrementer(void *pc) {
 
     calltree_update_clock();
 
+    gdk_threads_leave ();
+
     sleep(1);
   }
 }