Add a GMount::pre-unmount signal

This is the per-mount analogon to GVolumeMonitor::mount-pre-unmount.

gio/gmount.c

@@ -141,6 +141,22 @@ g_mount_base_init (gpointer g_class)
                     NULL, NULL,
                     g_cclosure_marshal_VOID__VOID,
                     G_TYPE_NONE, 0);
+     /**
+      * GMount::pre-unmount:
+      * @mount: the object on which the signal is emitted
+      *
+      * This signal is emitted when the #GMount is about to be
+      * unmounted.
+      *
+      * Since: 2.22.
+      **/
+      g_signal_new (I_("pre-unmount"),
+                    G_TYPE_MOUNT,
+                    G_SIGNAL_RUN_LAST,
+                    G_STRUCT_OFFSET (GMountIface, pre_unmount),
+                    NULL, NULL,
+                    g_cclosure_marshal_VOID__VOID,
+                    G_TYPE_NONE, 0);
 
       initialized = TRUE;
     }