[gtk+] gtkactiongroup: clarify set_translation_domain docs

[Diego Escalante Urrelo <diegoe src gnome org>]

commit a0f6fc137b81b1cecd012b47419de6144bce5658
Author: Diego Escalante Urrelo <diegoe igalia com>
Date:   Wed Feb 8 03:27:39 2012 -0500

    gtkactiongroup: clarify set_translation_domain docs
    
    NULL is an actual useful value for
    gtk_action_group_set_translation_domain, but this information is buried
    in g_dgettext() documentation.
    
    Be extra redundant, to make it obvious that NULL is ok.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=669636

 gtk/gtkactiongroup.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkactiongroup.c b/gtk/gtkactiongroup.c
index cb16e44..4c03b75 100644
--- a/gtk/gtkactiongroup.c
+++ b/gtk/gtkactiongroup.c
@@ -1406,7 +1406,8 @@ dgettext_swapped (const gchar *msgid,
 /**
  * gtk_action_group_set_translation_domain:
  * @action_group: a #GtkActionGroup
- * @domain: the translation domain to use for g_dgettext() calls
+ * @domain: (allow-none): the translation domain to use for g_dgettext()
+ * calls, or %NULL to use the domain set with textdomain()
  * 
  * Sets the translation domain and uses g_dgettext() for translating the 
  * @label and @tooltip of #GtkActionEntry<!-- -->s added by