[gtk+] Document help overlay action name in GtkApplication

[Phillip Wood <pwood src gnome org>]

commit c38c3361ca2b8aa1804cafddf22c4f074fc8b996
Author: Phillip Wood <phillip wood dunelm org uk>
Date:   Wed Feb 17 10:07:02 2016 +0000

    Document help overlay action name in GtkApplication
    
    This means all the information needed to automatically load a
    shortcuts window and create a menu item to show it is in one place.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=761431

 gtk/gtkapplication.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkapplication.c b/gtk/gtkapplication.c
index 3828738..ce023a2 100644
--- a/gtk/gtkapplication.c
+++ b/gtk/gtkapplication.c
@@ -96,11 +96,12 @@
  * resources.  See gtk_icon_theme_add_resource_path() for more
  * information.
  *
- * If there is a resource located at "gtk/help-overlay.ui" which is
- * defining a #GtkShortcutsWindow with ID "help_overlay" then GtkApplication
+ * If there is a resource located at "gtk/help-overlay.ui" which
+ * defines a #GtkShortcutsWindow with ID "help_overlay" then GtkApplication
  * associates an instance of this shortcuts window with each
  * #GtkApplicationWindow and sets up keyboard accelerators (Control-F1
- * and Control-?) to open it.
+ * and Control-?) to open it. To create an menu item that displays the
+ * shortcuts window associate the item with the action win.show-help-overlay.
  *
  * ## A simple application ## {#gtkapplication}
  *