Log Message:
mate-notification-daemon: update to 1.21.0:

### mate-notification-daemon 1.21.0

  * Translations update
  * Drop dbus-glib dependence
  * Use GVariant
  * Migrate from dbus-glib to GDBus
  * Add signals, remove annotation from xml file
  * Use gdbus generate files
  * Fix some gdk deprecations
  * src/daemon/daemon.c: Replace deprecated gvfs-open call by "gio \ 
open" from libglib2.0-bin.