libmm-glib,manager: register DBus error associations in advance

In order to have a proper conversion between DBus error names and GErrors for
our known domains, the associations need to be registered before any DBus
call attempt.

Given that the high-level API of libmm-glib has its entry point always in the
MMManager, just register them as soon as the first such object is created.

libmm-glib/mm-manager.c

@@ -595,9 +595,28 @@ initable_init_async (GAsyncInitable      *initable,
 
 /*****************************************************************************/
 
+static void
+register_dbus_errors (void)
+{
+  static volatile guint32 aux = 0;
+
+  if (aux)
+      return;
+
+  /* Register all known own errors */
+  aux |= MM_CORE_ERROR;
+  aux |= MM_MOBILE_EQUIPMENT_ERROR;
+  aux |= MM_CONNECTION_ERROR;
+  aux |= MM_SERIAL_ERROR;
+  aux |= MM_MESSAGE_ERROR;
+  aux |= MM_CDMA_ACTIVATION_ERROR;
+}
+
 static void
 mm_manager_init (MMManager *manager)
 {
+    register_dbus_errors ();
+
     /* Setup private data */
     manager->priv = G_TYPE_INSTANCE_GET_PRIVATE ((manager),
                                                  MM_TYPE_MANAGER,