[atk] doc: Improve AtkObject::children-changed documentation

[Alejandro Piñeiro Iglesias <apinheiro src gnome org>]

commit 650b164e5f0363c27c81849285fa6354245c5297
Author: Alejandro Piñeiro <apinheiro igalia com>
Date:   Thu Oct 24 12:25:50 2013 +0200

    doc: Improve AtkObject::children-changed documentation
    
    Specifically, adding the possibility to use NULL as the value for
    the child if it is removed.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=684667

 atk/atkobject.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/atk/atkobject.c b/atk/atkobject.c
index ed383b4..320472c 100755
--- a/atk/atkobject.c
+++ b/atk/atkobject.c
@@ -583,8 +583,11 @@ atk_object_class_init (AtkObjectClass *klass)
    * @atkobject: the object which received the signal.
    * @arg1: The index of the added or removed child. The value can be
    * -1. This is used if the value is not known by the implementor
-   * when the child is added or irrelevant.
-   * @arg2: A gpointer to the child AtkObject which was added or removed
+   * when the child is added/removed or irrelevant.
+   * @arg2: A gpointer to the child AtkObject which was added or
+   * removed. If the child was removed, it is possible that it is not
+   * available for the implementor. In that case this pointer can be
+   * NULL.
    *
    * The signal "children-changed" is emitted when a child is added or
    * removed form an object. It supports two details: "add" and