[nautilus] eel: gtk-extensions: readd removed function prototype

[Ernestas Kulik <ernestask src gnome org>]

commit 971b90d6467dc92b40b20ce4c8df11d986089cc7
Author: Ernestas Kulik <ernestask gnome org>
Date:   Sat Jan 20 23:31:18 2018 +0200

    eel: gtk-extensions: readd removed function prototype
    
    f0df1fc510bcc1007256612380a85d2373b66552 removed the prototype of a
    function that is still being used.

 eel/eel-gtk-extensions.h | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/eel/eel-gtk-extensions.h b/eel/eel-gtk-extensions.h
index 4fb5b20c7..1efb9b3d8 100644
--- a/eel/eel-gtk-extensions.h
+++ b/eel/eel-gtk-extensions.h
@@ -29,6 +29,9 @@
 #include <gdk-pixbuf/gdk-pixbuf.h>
 #include <gtk/gtk.h>
 
+/* GtkWindow */
+char *                eel_gtk_window_get_geometry_string              (GtkWindow            *window);
+
 /* GtkMenu and GtkMenuItem */
 GtkMenuItem *         eel_gtk_menu_append_separator                   (GtkMenu              *menu);
 GtkMenuItem *         eel_gtk_menu_insert_separator                   (GtkMenu              *menu,