[gtk] Popover: Minimally document the ::closed signal

[Daniel Boles <dboles src gnome org>]

commit 31b8e0f109d10c0eba0426da694d8730cd4b3036
Author: Daniel Boles <dboles src gmail com>
Date:   Mon Nov 5 23:36:54 2018 +0000

    Popover: Minimally document the ::closed signal
    
    This is better than nothing at all. The wording is taken from Carlos's
    commit message when he added this shortly before 3.12 (but skip Since).
    Skip the bit from his commit message explaining what this replaced; we
    don't need to say all the less good things our convenience API replaces.

 gtk/gtkpopover.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/gtk/gtkpopover.c b/gtk/gtkpopover.c
index cbfa3c9976..94f234c223 100644
--- a/gtk/gtkpopover.c
+++ b/gtk/gtkpopover.c
@@ -1650,6 +1650,12 @@ gtk_popover_class_init (GtkPopoverClass *klass)
 
   g_object_class_install_properties (object_class, NUM_PROPERTIES, properties);
 
+  /**
+   * GtkPopover::closed:
+   *
+   * This signal is emitted when the popover is dismissed either through
+   * API or user interaction.
+   */
   signals[CLOSED] =
     g_signal_new (I_("closed"),
                   G_TYPE_FROM_CLASS (object_class),