dbus: Add org.freedesktop.ScreenSaver.SimulateUserActivity support.

src/core/linux/SDL_dbus.c

@@ -310,7 +310,9 @@ SDL_DBus_QueryProperty(const char *node, const char *path, const char *interface
 void
 SDL_DBus_ScreensaverTickle(void)
 {
+    /* org.gnome.ScreenSaver is the legacy interface, but it'll either do nothing or just be a second harmless tickle on newer systems, so we leave it for now. */
     SDL_DBus_CallVoidMethod("org.gnome.ScreenSaver", "/org/gnome/ScreenSaver", "org.gnome.ScreenSaver", "SimulateUserActivity", DBUS_TYPE_INVALID);
+    SDL_DBus_CallVoidMethod("org.freedesktop.ScreenSaver", "/org/freedesktop/ScreenSaver", "org.freedesktop.ScreenSaver", "SimulateUserActivity", DBUS_TYPE_INVALID);
 }
 
 SDL_bool