Fix build with older GLib

Turns out g_strv_equal is recent.

testsuite/gtk/action.c

@@ -72,6 +72,27 @@ menu_item_label_notify_count (ActionTest    *fixture,
   g_object_unref (item);
 }
 
+#if !GLIB_CHECK_VERSION(2,60,0)
+gboolean
+g_strv_equal (const gchar * const *strv1,
+              const gchar * const *strv2)
+{
+  g_return_val_if_fail (strv1 != NULL, FALSE);
+  g_return_val_if_fail (strv2 != NULL, FALSE);
+
+  if (strv1 == strv2)
+    return TRUE;
+
+  for (; *strv1 != NULL && *strv2 != NULL; strv1++, strv2++)
+    {
+      if (!g_str_equal (*strv1, *strv2))
+        return FALSE;
+    }
+
+  return (*strv1 == NULL && *strv2 == NULL);
+}
+#endif
+
 static void
 g_test_action_muxer (void)
 {